Moving image coding method and moving image decoding method

ABSTRACT

A moving picture coding apparatus ( 10   a ) according to the present invention includes a level analyzer ( 100   a ) that decides the maximum number of intra frame pixels which can be coded (Nfpx) and the maximum number of storage pixels which can be stored in a picture memory of a decoding apparatus (Nspx) on the basis of a level identifier (Lst) indicating a coding level that is designated by the user, thereby judging whether coding of an input image is possible or not and calculating the maximum number of reference pictures (Nrpn) as the number of reference candidate pictures which can be referred to at inter picture prediction coding, on the basis of the maximum number of intra frame pixels (Nfpx) and the input image size (the number of vertical pixels (Nhpx) and the number of horizontal pixels (Nwpx)). A decoding apparatus to which a bit stream from the moving picture coding apparatus ( 10   a ) is supplied can always decode the bit stream satisfactorily, and perform inter picture prediction decoding corresponding to the inter picture prediction coding on the coding end. Consequently, memory areas of a coding apparatus and a decoding apparatus that are adapted to a coding method in which there is no restraint on the capacity of the memory area can be designed.

TECHNICAL FIELD

[0001] The present invention relates to a moving picture coding methodand a moving picture decoding method and, more particularly, to a codingmethod for coding digital data of moving pictures which are to betransmitted or stored, and a decoding method corresponding to the codingmethod.

BACKGROUND ART

[0002] A moving picture consists of a plurality of pictures, and eachpicture consists of a predetermined number of pixels. Coding of a movingpicture is carried out for each picture, and coding of each picture iscarried out with taking a block which is obtained by partitioning thepicture as a unit.

[0003] Generally, coding of a moving picture carries out compression ofinformation amount by eliminating redundancy in time direction and inspace direction.

[0004] For example, an inter picture prediction coding aiming ateliminating temporal redundancy carries out motion estimation and motioncompensation for the target picture which is to be coded in block unitswith referring to pictures which are located temporally forward orbackward of the target picture to generate prediction information, andthen codes the difference between the prediction information and thetarget picture information. A picture which is located temporallyforward of the target picture is a preceding picture, which is displayedearlier than the target picture, while a picture which is locatedtemporally backward of the target picture is a following picture, whichis displayed later than the target picture.

[0005] The H.264 coding system which is now being standardized as amoving picture coding system carries out motion compensation withrespect to the target picture with referring to arbitrary two pictureswhich are located temporally forward and backward of the target picture.The H.264 is numbered as a recommendation number by ITU-T (InternationalTelecommunication Union-Telecommunication Standardization Sector).

[0006] The coding aiming at eliminating spatial redundancy is carriedout using coding information of the coded blocks which were alreadycoded and which are positioned surrounding the target block.

[0007] However, when designing a coding apparatus and a decodingapparatus according to the H.264 system, there arises a problem that itis not possible to appropriately decide the sizes of the memory areaswhich are required in these apparatus. This is caused by that the degreeof freedom concerning the number of reference pictures which arereferred at inter picture prediction coding is extremely high.

[0008] Generally, in the coding method for a moving picture whichconsists of plural pictures, coding of a moving picture is carried outfor each picture, and coding of each picture is carried out with takinga block which is obtained by dividing the picture (hereinafter, referredto as macroblock) as a unit.

[0009] For example, the coding of a picture P is carried out for eachmacroblock MB constituting the pictureP, successively along an arrow Bas shown in FIG. 24(a). Further, coding of the macroblock MB12 as atarget block is carried out by predicting information such as motionvector, i.e., coding information, for the target macroblock withreferring to the coding information for macroblocks MB3, MB4, MB5, andMB12 which are located at above and at sides of the target macroblockMB12.

[0010] Therefore, it is necessary to hold the coding information of suchas the above macroblocks MB3 to MB11 which are located at above and atside of the target macroblock MB12 in order to perform prediction ofcoding information in coding macroblocks which are coded lately relativeto the macroblock 12 until the coding process for the target macroblockMB12 is completed. In other words, in coding processing for eachpicture, coded information of macroblocks of approximately one row arealways held. Therefore, in a case where the target image is an imagethat is laterally long, i.e., long in the horizontal direction, thecoded information which is to be held in the coding processing becomeslarge. Accordingly, when designing an apparatus which can perform codingof an image that is laterally long, i.e., long in the horizontaldirection, it is required to secure a large memory area for storing thecoding information. Meanwhile, the coding information of macroblocks MB1and MB2 shown in FIG. 24(b) are not referred to at coding of amacroblock whose coding order follows the macroblock MB12.

[0011] It is needless to say that a larger storage area for storing thecoding information, is required also when designing a decoding apparatusthat can decode an image having a longer lateral side, similarly as whendesigning a coding apparatus.

[0012] In the H.264 coding system, however, no requirements arecurrently imposed on images for their pixel numbers in the horizontaland vertical direction. This leads to a situation where the minimum sizefor a storage area that is required for appropriately performing codingor decoding of an image according to the H.264 standard is not decided.

[0013] In addition, when inter picture prediction coding or decoding isperformed according to the H.264 standard, it is required to store allpreceding and following pictures which are likely to be referred to in apicture memory.

[0014] To be brief, in the conventional MPEG (Moving Picture ExpertsGroup)-2 or MPEG-4 method, pictures which can be referred to at theinter picture prediction coding or inter picture prediction decoding,i.e., reference candidate picture, are shared by all blocks of thetarget picture to be coded or decoded. For example, when the targetpicture is a B picture which can refer to two other processed picturesat maximum, pictures which are referred to at coding or decoding of eachblock, i.e., reference pictures, are selected from two referencecandidate pictures that are decided for the target picture. When thetarget picture is a P picture which can refer to only one processedpicture, only a reference picture which is decided for the targetpicture, is used as a picture that is referred to at coding or decodingof each block.

[0015] Descriptions of the reference pictures are given in a followingpart of the MPEG-4 Standard:

[0016] ISO/IEC 14496-2:1999(E)

[0017] Information technology—coding of audio-visual objects

[0018] Part 2: Visual (1999-12-01)

[0019] PP.328, 329 Annex N

[0020] On the other hand, in the H.264 coding method, a picture that isreferred to at the inter picture prediction coding or inter pictureprediction decoding, i.e., a reference picture, is selected from pluralprocessed pictures whose image data are stored in a picture memory, foreach block in a target picture to be coded or decoded. For example, in acase where the target picture is a B picture, for which each block iscoded or decoded with referring to two other processed pictures atmaximum, two pictures at maximum which are selected from pluralprocessed pictures image data of which are stored in a picture memory,are referred to at coding or decoding of each block as referencepictures. In a case where the target picture is a P picture, for whicheach block is coded or decoded with referring to only one processedpicture, a picture which is selected from plural processed picturesimage data of which are stored in the picture memory is employed as apicture to be referred to at coding or decoding of each block, as areference picture.

[0021] As discussed above, according to the MPEG-2 or MPEG-4 method,when the target picture is a P picture, one processed picture is acandidate for the reference picture, i.e., a reference candidatepicture, and when the target picture is a B picture, two processedpictures are reference candidate pictures, while according to the H.264method, both in cases where the target picture is a P picture and wherethe target picture is a B picture, plural processed pictures whose imagedata are stored in the picture memory, serve as candidates for thereference picture, i.e., reference candidate pictures.

[0022]FIG. 25 is a diagram for explaining a specific control of apicture memory according to the H.264 system. FIG. 25 shows a case wherea picture memory can hold image data of four pictures. That is, in thiscase, three pictures among these four pictures, other than a targetpicture to be processed, are reference candidate pictures that may bereferred to.

[0023] For example, when inter picture prediction coding or interpicture prediction decoding is carried out with taking picture P5 as atarget picture to be processed as shown in FIG. 25, pictures P2 to P4whose image data are stored in a picture memory Mpt are adopted asreference candidate pictures. Here, pictures P1 to P5 are arranged incoding order (or decoding order), and these pictures are coded ordecoded in the order of arrangement. Thus, pictures which are displayedearlier than the target picture P5 among the reference candidatepictures P2 to P4, are preceding pictures for the target picture P5, andpictures which are displayed later than the target picture P5 among thereference candidate pictures P2 to P4, are following pictures for thetarget picture P5.

[0024] In a decoding apparatus, even when a previously decoded pictureis a decoded picture that is other than reference candidate pictureswhich are employed for referring in the inter picture predictiondecoding for the target picture, i.e., a decoded picture that is notemployed as a reference picture, image data of the decoded picture mustbe stored in a picture memory as a display waiting picture until theorder of display comes.

[0025]FIG. 26 are diagrams schematically showing the display waitpictures. FIG. 26(a) shows plural pictures constituting a movingpicture, which are pictures that may be used as reference pictures(reference candidate pictures) [used], and pictures that would not beused as reference pictures [unused]. FIG. 26(b) shows the relationshipbetween the decoding timing and the display timing of each picture.

[0026] For the purpose of illustration, FIG. 26 show a case wherereference pictures [used] which are used at coding or decoding of eachblock in B picture are both or either of two reference candidatepictures that are commonly used for all blocks in this B picture, andreference pictures [used] which are used at the coding or decoding ofeach block in P picture are one reference candidate picture that iscommonly used for all blocks in this P picture. However, in the H.264method, a picture to be referred to at picture coding or decoding, i.e.,a reference picture, is selected from plural processed pictures whoseimage data are stored in picture memory, for each block of a targetpicture to be coded or decoded. Therefore, the reference candidatepictures which are used at coding or decoding of B picture are notrestricted to two specific pictures for each B picture as shown in FIG.26(a), and the reference candidate picture that is used at coding ordecoding of P picture is not restricted to one specific picture for eachP picture as shown in FIG. 26(a).

[0027] In FIG. 26(a), reference candidate pictures for B picture B1 arean I picture I0 and B picture B2, and reference candidate pictures for Bpicture B2 are I picture I0 and P picture P4. Further, referencecandidate pictures for B picture B3 are B picture B2 and P picture P4,and a reference candidate picture for P picture P8 is P picture P4.

[0028]FIG. 26(b) shows that respective pictures shown in FIG. 26(a) aredecoded in the order of pictures I0, P4, B2, B1, B3, P8, B6, B5, B7, andthen displayed in the order of pictures I0, B1, B2, B3, P4, B5, B6, B7,P8.

[0029] In FIG. 26(b), Tdec shows the time axis for representing thedecoding times of respective pictures, and Tdsp shows the time axis forrepresenting the display times of respective pictures. In addition,tdec(0), tdec(1), tdec(2), tdec(3), tdec(4), tdec(5), tdec(6), tdec(7),and tdec(8) denote the time periods in which decoding of pictures I0,B1, B2, B3, P4, B5, B6, B7, and P8 are carried out, respectively.Further, tdsp (0), tdsp(1), tdsp(2), tdsp(3), tdsp(4), tdsp(5), tdsp(6),tdsp(7), and tdsp(8) denote the time periods in which display ofpictures I0, B1, B2, B3, P4, B5, B6, B7, and P8 are carried out,respectively.

[0030] In this case, the decoding times of the pictures B2, B1, B3, P8,B6, B5 and B7 roughly coincide with the display times of the picturesI0, B1, B2, B3, P4, B5, and B6, respectively, as shown in FIG. 26(b). Inaddition, the control of the picture memory is performed so that imagedata of decoded pictures are stored in the picture memory, and the imagedata of the pictures are deleted successively from pictures which havebeen displayed.

[0031] In this case, for example, I picture I0 is displayed afterwaiting for the B picture B2 being decoded.

[0032] The image data of the reference candidate pictures are stored inthe picture memory, and these pictures are employed as referencepictures until these pictures are displayed later. However, image dataof pictures that are not referred to also must be kept until thesepictures are displayed after being decoded. The image data of suchdecoded pictures that are not employed as reference pictures, are storedin a predetermined memory as display waiting pictures until thesepictures are displayed.

[0033] In FIG. 26(a), B picture B1 that is decoded after I picture I0being decoded, is a picture that is not used as a reference picture andwill be displayed subsequent to I picture I0, and therefore, it can bedisplayed immediately after the decoding thereof, while B picture B3that is decoded after B picture B1 being decoded, is a picture that willbe displayed after B picture B2 being displayed, that follows B pictureB1, and therefore, it will be displayed with waiting for a displayperiod of one picture, i.e., B picture B2, after B picture B1 beingdecoded.

[0034] In this case, the number of display waiting picture(s) at thedecoding start timing of P picture P8 is only one, i.e., B picture B3.

[0035] Further, there arises no problem by that the image data ofpictures which will not be used as reference pictures should be deletedimmediately after the display of those pictures is completed. However,the timing of deleting the image data of these pictures may be otherthan immediately after the display of those pictures being performed.

[0036] In such cases, the image data of the pictures which are not usedas reference pictures, would be kept stored in the memory also afterthese pictures are displayed, and these pictures whose image data areheld in the picture memory are also handled as display waiting pictures.

[0037] For example, in a case where the control of the picture memory iscarried out such that image data of a picture which is stored in thepicture memory but is not used as a reference picture, is deleted fromthe picture memory after a display time of one picture expiring afterthe picture was displayed, the number of display waiting pictures at thestart of decoding of P picture P8 amounts to two, i.e., B picture B2 andB picture B3.

[0038] As discussed above, plural decoded or coded pictures are storedin a picture memory of a decoding apparatus or a coding apparatus, whilein the H.264 coding system there is currently no limitations on themaximum number of reference candidate pictures which are employed at theinter picture prediction coding or decoding, i.e., the maximum referencepicture number.

[0039] Thus, in the design of a coding apparatus or a decoding apparatusaccording to the H.264 system, the maximum number of decoded or codedpictures which are to be stored in the picture memory cannot beestablished, and therefore the capacity of a storage area to be mountedin the apparatus cannot be decided.

[0040] The present invention is made to solve the above-mentionedproblems, and has for its object to provide a moving picture codingmethod and a moving picture decoding method which can correctly judgethe capability/incapability of coding or decoding for a moving pictureas well as efficiently utilize a memory area mounted in acoding/decoding apparatus, and thereby enables designing a memory areain a coding/decoding apparatus according to a coding method whichimposes no limitations on the capacity of the memory.

DISCLOSURE OF THE INVENTION

[0041] According to the present invention (claim 1), there is provided amethod for coding a moving picture which consists of a plurality ofpictures each consisting of a prescribed number of pixels, according toa selected coding level, including: a step of judging whether it ispossible to code the moving picture, on the basis of the maximum numberof intra frame pixels for a picture, which number conforms with theselected coding level; and a step of coding the moving picture that hasbeen judged encodable in the judging step, for each picture, to generatea code sequence for the moving picture, in which the code sequenceincludes a code of a level identifier that identifies the maximum numberof intra frame pixels for a picture that conforms with the selectedcoding level, and the maximum number of storage pixel numbercorresponding to the data amount that can be stored in a picture memory,which conforms with the selected coding level, and the vertical pixelnumber and the horizontal pixel number of a picture constituting themoving picture that has been judged encodable in the judgement stepsatisfy predetermined conditions dependent on the level identifier.

[0042] According to the present invention (claim 2), in the movingpicture coding method of claim 1, the coding step performs an interpicture prediction coding to a target picture to be coded, using a codedpicture as a reference picture, where the maximum reference picturenumber that is the maximum number of reference candidate picturesserving as candidates for the reference picture, which pictures can bestored in the picture memory, is calculated on the basis of the verticalpixel number and the horizontal pixel number of the target picture aswell as the level identifier.

[0043] According to the present invention (claim 3), in the movingpicture coding method of claim 1, the vertical pixel number (h) and thehorizontal pixel number (w) of a picture included in the moving picturethat has been judged encodable satisfy all following conditions, i.e.,(condition 1) to (condition 3):

[0044] (condition 1) h×w<=(the maximum number of intra frame pixelnumber)

[0045] (condition 2) h<=round1 (H)

[0046] (condition 3) w<=round2 (W)

[0047] where H denotes the maximum number among vertical pixel numbersin the picture which can be coded, W denotes the maximum number amonghorizontal pixel numbers in the picture which can be coded, round1( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the vertical pixel number in amacroblock which is a unit for coding a picture, and round2( ) denotes avalue that is obtained by an operation of rounding an argument inparentheses to a multiple of the horizontal pixel number in themacroblock.

[0048] According to the present invention (claim 4), in the movingpicture coding method of claim 3, round1( ) and round2( ) each denotes avalue which is obtained by an operation of rounding an argument inparentheses to a multiple of 16.

[0049] According to the present invention (claim 5), in the movingpicture coding method of claim 2, the maximum reference picture numberfor the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1

[0050] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, and themaximum storage pixel number is the total number of the pixel numbers ofthe reference candidate pictures and of the target picture to bedecoded, which pictures are stored in a picture memory in the decodingapparatus.

[0051] According to the present invention (claim 6), in the movingpicture coding method of claim 2, the maximum reference picture numberfor the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1−(the number of display waiting decoded pictures)

[0052] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, and themaximum storage pixel number is the total number of the pixel numbersof, reference candidate pictures, the target picture to be decoded, anddisplay waiting decoded pictures, which pictures are stored in a picturememory of the decoding apparatus.

[0053] According to the present invention (claim 7), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are calculated using following twoformulae:

H=sqrt (h×w×N)

W=sqrt (h×w×N),

[0054] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, H denotesthe maximum number among the vertical pixel numbers over pictures whichcan be coded, W denotes the maximum number among the horizontal pixelnumbers over the pictures which can be coded, N denotes an arbitrarynatural number, and sqrt( ) denotes a positive square root of anargument in parentheses.

[0055] According to the present invention (claim 8), in the movingpicture coding method of claim 7, the natural number N is 8.

[0056] According to the present invention (claim 9), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are calculated using following twoformulae:

H=(the maximum intra frame pixel number)÷(vertical pixel numbercalculation coefficient)

W=(the maximum intra frame pixel number)÷(horizontal pixel numbercalculation coefficient)

[0057] where H denotes the maximum vertical pixel number among pictureswhich can be coded, W denotes the maximum horizontal pixel number amongpictures which can be coded, and the vertical pixel number calculationcoefficient and the horizontal pixel number calculation coefficient arepredetermined values.

[0058] According to the present invention (claim 10), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are decided with referring to apreviously defined table.

[0059] According to the present invention (claim 11), there is provideda method for decoding a code sequence corresponding to a moving picturewhich consists of plural pictures each consisting of a prescribed numberof pixels, in accordance with a level identifier for identifying aselected coding level, which is extracted from the code sequence,including: a step of judging whether it is possible to decode the codesequence or not, on the basis of the maximum intra frame pixel numberfor a picture, which number is dependent on the coding level indicatedby the level identifier, and the maximum storage pixel number which isan amount of data which can be stored in a picture memory and isdependent on the coding level; and a step of decoding the code sequencethat has been judged encodable in the judgement step, for each picture,to generate image data for the moving picture, in which the verticalpixel number and the horizontal pixel number of a picture presented bythe code sequence that has been judged decodable in the judgement stepsatisfy predetermined conditions which are provided according to thelevel identifier.

[0060] According to the present invention (claim 12), in the movingpicture decoding method of claim 11, the judgment step performs judgmentof whether it is possible to decode the target code sequence or not, onthe basis of the result of comparison between unique conditions providedin the decoding apparatus, and the maximum intra frame pixel number andthe maximum storage pixel number both corresponding to the coding levelindicated by the level identifier which is extracted from the codesequence.

[0061] According to the present invention (claim 13), in the movingpicture decoding method of claim 11, the decoding step subjects a targetcode sequence to an inter picture prediction decoding, using decodedpictures as reference pictures, and the maximum reference picture numberwhich is the maximum number of reference candidate pictures serving as acandidate for a reference picture, which can be stored in the picturememory, is calculated on the basis of the vertical pixel number and thehorizontal pixel number for the target picture as well as the levelidentifier.

[0062] According to the present invention (claim 14), in the movingpicture decoding method of claim 11, the vertical pixel number (h) andthe horizontal pixel number (w) of a picture corresponding to the bitstream that has been judged decodable satisfy all following conditions,i.e., (condition 4) to (condition 6):

[0063] (condition 4) h<=round1 (H)

[0064] (condition 5) w<=round2 (W)

[0065] (condition 6) h×w<=(the maximum intra frame pixel number)

[0066] where H denotes the maximum number among vertical pixel numbersof pictures that can be decoded, W denotes the maximum number amonghorizontal pixel numbers of pictures that can be decoded, round1( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the vertical pixel number in amacroblock serving as a unit for decoding a picture, and round2( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the horizontal pixel number in theabove-described macroblock.

[0067] According to the present invention (claim 15), in the movingpicture decoding method of claim 14, round1( ) and round2( ) eachdenotes a value which is obtained by an operation of rounding anargument in parentheses to a multiple of 16.

[0068] According to the present invention (claim 16), in the movingpicture decoding method of claim 12, the maximum reference picturenumber for the target picture is determined by following formulae:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1

[0069] where h denotes the vertical pixel number in the target pictureto be decoded, w denotes the horizontal pixel number in the targetpicture to be decoded, and the maximum storage pixel number denotes thetotal number of, the pixel numbers of the reference candidate picturesand the pixel number of the target picture to be decoded, these picturesbeing stored in a picture memory of the decoding apparatus.

[0070] According to the present invention (claim 17), in the movingpicture decoding method of claim 12, the maximum reference picturenumber for the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1−(the number of display waiting decoded pictures)

[0071] where h denotes the vertical pixel number in the target pictureto be decoded, w denotes the horizontal pixel number in the targetpicture to be decoded, and the maximum storage pixel number is the totalnumber of the pixel numbers of, the reference candidate pictures, thetarget picture to be decoded, and display waiting decoded pictures,these pictures being stored in a picture memory of the decodingapparatus.

[0072] According to the present invention (claim 18), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are calculated using followingtwo formulae:

H=sqrt (h×w×N)

W=sqrt (h×w×N),

[0073] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, H denotesthe maximum number among vertical pixel numbers of pictures which can bedecoded, W denotes the maximum number among horizontal pixel numbers ofpictures which can be decoded, N denotes an arbitrary natural number,sqrt( ) denotes a positive square root of an argument in parentheses.

[0074] According to the present invention (claim 19), in the movingpicture decoding method of claim 18, the natural number N is 8.

[0075] According to the present invention (claim 20), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are calculated using followingtwo formulae:

H=(the maximum intra frame pixel number)÷(vertical pixel numbercalculation coefficient)

W=(the maximum intra frame pixel number)÷(horizontal pixel numbercalculation coefficient)

[0076] where H denotes the maximum number among vertical pixel numbersin pictures which can be decoded, and W denotes the maximum number amonghorizontal pixel numbers in pictures which can be decoded.

[0077] According to the present invention (claim 21), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are decided with referring to apreviously defined table.

[0078] According to the present invention (claim 22), there is provideda data storage medium that contains a program for implementing a processof coding a moving picture, where the program makes a computer executethe coding process according to the moving picture coding method of anyof claims 1 to 10.

[0079] According to the present invention (claim 23), there is provideda data storage medium that contains a program for implementing a processof decoding a code sequence corresponding to a moving picture, where theprogram makes a computer execute the decoding process according to themoving picture decoding method of any of claims 11 to 21.

[0080] As described above, according to the present invention (claim 1),there is provided a method for coding a moving picture which consists ofa plurality of pictures each consisting of a prescribed number ofpixels, according to a selected coding level, including: a step ofjudging whether it is possible to code the moving picture, on the basisof the maximum number of intra frame pixels for a picture, which numberconforms with the selected coding level; and a step of coding the movingpicture that has been judged encodable in the judging step, for eachpicture, to generate a code sequence for the moving picture, in whichthe code sequence includes a code of a level identifier that identifiesthe maximum number of intra frame pixels for a picture that conformswith the selected coding level, and the maximum number of storage pixelnumber corresponding to the data amount that can be stored in a picturememory, which conforms with the selected coding level, and the verticalpixel number and the horizontal pixel number of a picture constitutingthe moving picture that has been judged encodable in the judgement stepsatisfy predetermined conditions dependent on the level identifier.

[0081] Therefore, memory areas in a coding apparatus and a decodingapparatus which correspond to a coding method in which there is nolimitations on the capacity of the memory area can be designed.

[0082] In other words, according to the present invention, the maximumstorage pixel number and the maximum intra frame pixel number can be setat optimal values which are selected from plural values which aredefined stepwise, in accordance with specifications for the apparatus,thereby the capability/incapability of coding or decoding for a targetmoving picture as well as the maximum picture number that can bereferred to at inter picture prediction coding, can be easily decided onthe basis of conditional formulas and tables with utilizing the selectedmaximum storage pixel number and maximum intra frame pixel number.Thereby, indices associated with the design of the memory areas in thecoding apparatus and the decoding apparatus are given, leading to aneffective handling of the memory capacity with judging correctly thecapability/incapability of the coding or decoding which is to beexecuted to the target moving picture.

[0083] According to the present invention (claim 2), in the movingpicture coding method of claim 1, the coding step performs an interpicture prediction coding to a target picture to be coded, using a codedpicture as a reference picture, where the maximum reference picturenumber that is the maximum number of reference candidate picturesserving as candidates for the reference picture, which pictures can bestored in the picture memory, is calculated on the basis of the verticalpixel number and the horizontal pixel number of the target picture aswell as the level identifier. Therefore, the inter picture predictioncoding can be carried out with effectively utilizing a picture memory.

[0084] According to the present invention (claim 3), in the movingpicture coding method of claim 1, the vertical pixel number (h) and thehorizontal pixel number (w) of a picture included in the moving picturethat has been judged encodable satisfy all following conditions, i.e.,(condition 1) to (condition 3):

[0085] (condition 1) h×w<=(the maximum number of intra frame pixelnumber)

[0086] (condition 2) h<=round1 (H)

[0087] (condition 3) w<=round2 (W)

[0088] where H denotes the maximum number among vertical pixel numbersin the picture which can be coded, W denotes the maximum number amonghorizontal pixel numbers in the picture which can be coded, round1( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the vertical pixel number in amacroblock which is a unit for coding a picture, and round2( ) denotes avalue that is obtained by an operation of rounding an argument inparentheses to a multiple of the horizontal pixel number in themacroblock. Therefore, the capability or incapability of coding of amoving picture as an input image can be judged with reference to thenumbers of macroblocks in a picture as units of coding in the verticaland horizontal directions.

[0089] According to the present invention (claim 4), in the movingpicture coding method of claim 3, round1( ) and round2( ) each denotes avalue which is obtained by an operation of rounding an argument inparentheses to a multiple of 16. Therefore, the capability orincapability of the coding for a moving picture as an input image can bejudged with reference to the numbers of macroblocks as units of codingin a picture in the vertical and horizontal directions, each macroblockbeing composed of 16 pixels and 16 pixels.

[0090] According to the present invention (claim 5), in the movingpicture coding method of claim 2, the maximum reference picture numberfor the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1

[0091] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, and themaximum storage pixel number is the total number of the pixel numbers ofthe reference candidate pictures and of the target picture to bedecoded, which pictures are stored in a picture memory in the decodingapparatus. Therefore, an area for storing decoded data of a targetpicture can be always kept in the picture memory of the decodingapparatus.

[0092] According to the present invention (claim 6), in the movingpicture coding method of claim 2, the maximum reference picture numberfor the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1−(the number of display waiting decoded pictures)

[0093] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, and themaximum storage pixel number is the total number of the pixel numbersof, reference candidate pictures, the target picture to be decoded, anddisplay waiting decoded pictures, which pictures are stored in a picturememory of the decoding apparatus. Therefore, the number of referencecandidate pictures in a picture memory of a decoding apparatus can bechanged according to the number of display waiting decoded pictures.

[0094] According to the present invention (claim 7), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are calculated using following twoformulae:

H=sqrt (h×w×N)

W=sqrt (h×w×N),

[0095] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, H denotesthe maximum number among the vertical pixel numbers over pictures whichcan be coded, W denotes the maximum number among the horizontal pixelnumbers over the pictures which can be coded, N denotes an arbitrarynatural number, and sqrt( ) denotes a positive square root of anargument in parentheses. Therefore, the difference between the verticaldimension and the horizontal dimension of the input image can be keptwithin a predetermined range.

[0096] According to the present invention (claim 8), in the movingpicture coding method of claim 7, the natural number N is 8. Therefore,the ratio between the vertical dimension and the horizontal dimension ofthe input image can be kept within a range of 8:1 or smaller.

[0097] According to the present invention (claim 9), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are calculated using following twoformulae:

H=(the maximum intra frame pixel number)÷(vertical pixel numbercalculation coefficient)

W=(the maximum intra frame pixel number)÷(horizontal pixel numbercalculation coefficient)

[0098] where H denotes the maximum vertical pixel number among pictureswhich can be coded, W denotes the maximum horizontal pixel number amongpictures which can be coded, and the vertical pixel number calculationcoefficient and the horizontal pixel number calculation coefficient arepredetermined values. Therefore, the maximum vertical pixel number andthe maximum horizontal pixel number can be calculated by simpleoperations.

[0099] According to the present invention (claim 10), in the movingpicture coding method of claim 3, the maximum vertical pixel number andthe maximum horizontal pixel number are decided with referring to apreviously defined table. Therefore, the maximum vertical pixel numberand the maximum horizontal pixel number can be decided without employingan arithmetic operation.

[0100] According to the present invention (claim 11), there is provideda method for decoding a code sequence corresponding to a moving picturewhich consists of plural pictures each consisting of a prescribed numberof pixels, in accordance with a level identifier for identifying aselected coding level, which is extracted from the code sequence,including: a step of judging whether it is possible to decode the codesequence or not, on the basis of the maximum intra frame pixel numberfor a picture, which number is dependent on the coding level indicatedby the level identifier, and the maximum storage pixel number which isan amount of data which can be stored in a picture memory and isdependent on the coding level; and a step of decoding the code sequencethat has been judged encodable in the judgement step, for each picture,to generate image data for the moving picture, in which the verticalpixel number and the horizontal pixel number of a picture presented bythe code sequence that has been judged decodable in the judgement stepsatisfy predetermined conditions which are provided according to thelevel identifier. Therefore, the capability or incapability of decodingin a decoding apparatus can be judged correctly, leading to an efficienthandling of the storage capacity.

[0101] In other words, according to the present invention, the maximumstorage pixel number and the maximum intra frame pixel number can be setat optimal values that are selected from plural values which are definedstepwise, in accordance with specifications of the apparatus, wherebythe capability/incapability of coding or decoding of a target movingpicture, and the maximum picture number that can be referred to at interpicture prediction coding can be decided on the basis of conditionalformulas and tables, using the selected maximum storage pixel number andselected maximum intra frame pixel number.

[0102] Further, because the code sequence includes, as headerinformation, an identifier of a coding level corresponding to themaximum storage pixel number and the maximum intra frame pixel numberwhich have been selected on the coding end, the decoding apparatus canimmediately determine the coding level on the basis of the identifier ofthe coding level.

[0103] According to the present invention (claim 12), in the movingpicture decoding method of claim 11, the judgment step performs judgmentof whether it is possible to decode the target code sequence or not, onthe basis of the result of comparison between unique conditions providedin the decoding apparatus, and the maximum intra frame pixel number andthe maximum storage pixel number both corresponding to the coding levelindicated by the level identifier which is extracted from the codesequence. Therefore, it is possible to easily judge whether a codesequence that is inputted to a decoding apparatus can be decoded or notby the decoding apparatus.

[0104] According to the present invention (claim 13), in the movingpicture decoding method of claim 11, the decoding step subjects a targetcode sequence to an inter picture prediction decoding, using decodedpictures as reference pictures, and the maximum reference picture numberwhich is the maximum number of reference candidate pictures serving as acandidate for a reference picture, which can be stored in the picturememory, is calculated on the basis of the vertical pixel number and thehorizontal pixel number for the target picture as well as the levelidentifier. Therefore, the inter picture prediction coding can beexecuted with effectively utilizing the picture memory.

[0105] According to the present invention (claim 14), in the movingpicture decoding method of claim 11, the vertical pixel number (h) andthe horizontal pixel number (w) of a picture corresponding to the bitstream that has been judged decodable satisfy all following conditions,i.e., (condition 4) to (condition 6):

[0106] (condition 4) h<=round1 (H)

[0107] (condition 5) w<=round2 (W)

[0108] (condition 6) h×w<=(the maximum intra frame pixel number)

[0109] where H denotes the maximum number among vertical pixel numbersof pictures that can be decoded, W denotes the maximum number amonghorizontal pixel numbers of pictures that can be decoded, round1( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the vertical pixel number in amacroblock serving as a unit for decoding a picture, and round2( )denotes a value that is obtained by an operation of rounding an argumentin parentheses to a multiple of the horizontal pixel number in theabove-described macroblock. Therefore, the capability or incapability ofcoding for a moving picture as an input image can be judged withreference to the numbers of macroblocks as units of coding in a picturein the vertical and horizontal directions.

[0110] According to the present invention (claim 15), in the movingpicture decoding method of claim 14, round1( ) and round2( ) eachdenotes a value which is obtained by an operation of rounding anargument in parentheses to a multiple of 16. Therefore, thecapability/incapability of coding for a moving picture as an input imagecan be judged with reference to the numbers of macroblocks as units ofcoding in a picture in the vertical and horizontal directions, eachmacroblock being composed of 16 pixels×16 pixels.

[0111] According to the present invention (claim 16), in the movingpicture decoding method of claim 12, the maximum reference picturenumber for the target picture is determined by following formulae:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1

[0112] where h denotes the vertical pixel number in the target pictureto be decoded, w denotes the horizontal pixel number in the targetpicture to be decoded, and the maximum storage pixel number denotes thetotal number of, the pixel numbers of the reference candidate picturesand the pixel number of the target picture to be decoded, these picturesbeing stored in a picture memory of the decoding apparatus. Therefore,an area for storing decoded data of a target picture can be always keptin a picture memory of a decoding apparatus.

[0113] According to the present invention (claim 17), in the movingpicture decoding method of claim 12, the maximum reference picturenumber for the target picture is determined by a following formula:

(the maximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1−(the number of display waiting decoded pictures)

[0114] where h denotes the vertical pixel number in the target pictureto be decoded, w denotes the horizontal pixel number in the targetpicture to be decoded, and the maximum storage pixel number is the totalnumber of the pixel numbers of, the reference candidate pictures, thetarget picture to be decoded, and display waiting decoded pictures,these pictures being stored in a picture memory of the decodingapparatus. Therefore, the number of reference candidate pictures can bechanged according to the number of display waiting decoded pictures in apicture memory of a decoding apparatus.

[0115] According to the present invention (claim 18), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are calculated using followingtwo formulae:

H=sqrt (h×w×N)

W=sqrt (h×w×N)

[0116] where h denotes the vertical pixel number in the target picture,w denotes the horizontal pixel number in the target picture, H denotesthe maximum number among vertical pixel numbers of pictures which can bedecoded, W denotes the maximum number among horizontal pixel numbers ofpictures which can be decoded, N denotes an arbitrary natural number,sqrt( ) denotes a positive square root of an argument in parentheses.Therefore, a difference between the vertical dimension and thehorizontal dimension of an input image can be kept within apredetermined range.

[0117] According to the present invention (claim 19), in the movingpicture decoding method of claim 18, the natural number N is 8.Therefore, the ratio between the vertical dimension and the horizontaldimension of an input image can be kept within a range of 8:1 orsmaller.

[0118] According to the present invention (claim 20), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are calculated using followingtwo formulae:

H=(the maximum intra frame pixel number)÷(vertical pixel numbercalculation coefficient)

W=(the maximum intra frame pixel number)÷(horizontal pixel numbercalculation coefficient)

[0119] where H denotes the maximum number among vertical pixel numbersin pictures which can be decoded, and W denotes the maximum number amonghorizontal pixel numbers in pictures which can be decoded. Therefore,the maximum vertical pixel number and the maximum horizontal pixelnumber can be calculated by simple operations.

[0120] According to the present invention (claim 21), in the movingpicture decoding method of claim 14, the maximum vertical pixel numberand the maximum horizontal pixel number are decided with referring to apreviously defined table. Therefore, the maximum vertical pixel numberand the maximum horizontal pixel number can be decided without employingarithmetic operations.

[0121] According to the present invention (claim 22), there is provideda data storage medium that contains a program for implementing a processof coding a moving picture, where the program makes a computer executethe coding process according to the moving picture coding method of anyof claims 1 to 10. Therefore, by loading a program for implementing acoding process for a moving picture on a computer, it is possible toperform the handling of a memory area in a coding apparatus efficiently,thereby facilitating the design of the apparatus.

[0122] According to the present invention (claim 23), there is provideda data storage medium that contains a program for implementing a processof decoding a code sequence corresponding to a moving picture, where theprogram makes a computer execute the decoding process according to themoving picture decoding method of any of claims 11 to 21. Therefore, byloading a program for implementing a process for coding a moving pictureon a computer, it is possible to perform the handling of a memory areain a coding apparatus efficiently, thereby facilitating the design ofthe apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0123]FIG. 1 is a block diagram for explaining a moving picture codingapparatus 10 a according to a first embodiment of the present invention.

[0124]FIG. 2 is a block diagram illustrating a specific construction ofa coding capability judgment unit 108 a in the moving picture codingapparatus 10 a according to the first embodiment.

[0125]FIG. 3 is a block diagram illustrating a specific construction ofa maximum reference picture number calculation unit 109 a in the movingpicture coding apparatus 10 a according to the first embodiment.

[0126]FIG. 4 is a block diagram for explaining a moving picture codingapparatus 10 b according to a second embodiment of the presentinvention.

[0127]FIG. 5 is a block diagram illustrating a specific construction ofa coding capability judgment unit 108 b in the moving picture codingapparatus 10 b according to the second embodiment.

[0128]FIG. 6 is a block diagram for explaining a moving picture codingapparatus 10 c according to a third embodiment of the present invention.

[0129]FIG. 7 is a block diagram illustrating a specific construction ofa coding capability judgment unit 108 c in the moving picture codingapparatus 10 c according to the third embodiment.

[0130]FIG. 8 is a block diagram for explaining a moving picture codingapparatus 10 d according to a fourth embodiment of the presentinvention.

[0131]FIG. 9 is a block diagram illustrating a specific construction ofa maximum reference picture number calculation unit 109 d in the movingpicture coding apparatus 10 d according to the fourth embodiment.

[0132]FIG. 10 is a block diagram for explaining a moving picturedecoding apparatus 50 a according to a fifth embodiment of the presentinvention.

[0133]FIG. 11 is a block diagram for explaining a moving picturedecoding apparatus 50 b according to a sixth embodiment of the presentinvention.

[0134]FIG. 12 is a block diagram for explaining a moving picturedecoding apparatus 50 c according to a seventh embodiment of the presentinvention.

[0135]FIG. 13 is a block diagram for explaining a moving picturedecoding apparatus 50 d according to an eighth embodiment of the presentinvention.

[0136] FIGS. 14 are diagram for explaining data structures of bitstreams which are generated by the moving picture coding apparatusaccording to the above embodiments; FIGS. 14(a), 14(b), and 14(c)showing bit streams Bsa, Bsb, and Bsc, which are generated by the movingpicture coding apparatuses 10 a, 10 b, and 10 c according to the first,second, and third embodiments, respectively.

[0137]FIG. 15 is a diagram showing a table T1 that definescorrespondence between the level identifier and a pair of the maximumintra frame pixel number and the maximum storage pixel number, which isemployed in the moving picture coding apparatus 10 a according to thefirst embodiment.

[0138] FIGS. 16 are diagram showing tables which are employed in themoving picture coding apparatus 10 a according to the first embodiment;FIG. 16(a) showing a table T1 a that defines correspondence between thelevel identifier and the maximum intra frame pixel number, and FIG.16(b) showing a table T1 b that defines correspondence between the levelidentifier and the maximum storage pixel number.

[0139] FIGS. 17 are diagram showing tables which are employed in thesecond embodiment; FIG. 17(a) showing a table T2 that definescorrespondence between the identification number and a pair of thevertical pixel number calculation coefficient and the vertical pixelnumber calculation coefficient, FIG. 17(b) showing a table T2 a thatdefines correspondence between the identification number and thehorizontal pixel number calculation coefficient, and FIG. 17(c) showinga table T2 b that defines correspondence between the identificationnumber and the vertical pixel number calculation coefficient.

[0140] FIGS. 18 are diagram showing tables which are employed in thethird embodiment, FIG. 18(a) showing a table T3 that definescorrespondence between the identification number and a pair of themaximum vertical pixel number and the maximum horizontal pixel number,FIG. 18(b) showing a table T3 a that defines correspondence between theidentification number and the maximum horizontal pixel number, and FIG.18(c) showing a table T3 b that defines correspondence between theidentification number and the maximum vertical pixel number.

[0141]FIG. 19 are diagrams explaining a data storage medium thatcontains a program for implementing the moving picture coding apparatusor the moving picture decoding apparatus according to any of the aboveembodiments by a computer system (FIGS. 19(a) and 19(b)), and thecomputer system (FIG. 19(c)).

[0142]FIG. 20 is a diagram for explaining an application of the movingpicture coding apparatus and the moving picture decoding apparatusaccording to any of the above embodiments, and shows a contents supplysystem 1100 for providing contents distribution services.

[0143]FIG. 21 is a diagram for explaining a portable phone 1200 thatutilizes the moving picture coding apparatus and the moving picturedecoding apparatus according to any of the above embodiments.

[0144]FIG. 22 is a block diagram illustrating a specific construction ofthe portable phone 1200 as shown in FIG. 21.

[0145]FIG. 23 is a conceptual drawing showing a digital broadcastingsystem 1400 that utilizes the moving picture coding apparatus or themoving picture decoding apparatus according to any of the aboveembodiments.

[0146] FIGS. 24 are diagram for explaining a conventional coding method,and FIG. 24(a) showing the order of coding for macroblocks in a targetpicture to be coded, and FIG. 24(b) showing surrounding macroblockswhich are referred to at the coding of a target macroblock to be coded.

[0147]FIG. 25 is a diagram for explaining conventional coding method anddecoding method, and shows other pictures whose image data are stored ina picture memory at the coding (or decoding) of a target picture.

[0148]FIG. 26 are diagrams schematically showing the control for displaywait pictures in the conventional coding method and decoding method,FIG. 26(a) showing pictures which are referred to ([used]) and pictureswhich are not referred to ([unused]), and FIG. 26(b) showing therelationship between the decoding timing and the coding timing of eachpicture.

BEST MODE FOR CARRYING OUT THE INVENTION

[0149] Hereinafter, embodiments of the present invention will bedescribed.

[0150] [Embodiment 1]

[0151]FIG. 1 is a block diagram explaining a moving picture codingapparatus 10 a according to a first embodiment of the present invention.

[0152] The moving picture coding apparatus 10 a according to the firstembodiment divides plural pictures that constitute a moving picture,into predetermined data processing units, i.e., blocks, respectively,and encodes image data of each picture for each block. It is assumedhere that the block is a macroblock which is composed of 16 verticalpixels×16 horizontal pixels.

[0153] More specifically, this moving picture coding apparatus 10 aincludes a picture memory 101 that stores input data Id of a inputmoving picture which is inputted picture by picture, and outputs storeddata SId block by block; a difference calculator 113 that calculates adifference between the image data SId of a target block to be coded,which is outputted from the input picture memory 101 and predictive dataPd of the target block, and outputs prediction residual data Dd of thetarget block; and a prediction residual encoder 102 that compressivelyencodes the image data SId or prediction residual data Dd of the targetblock. Here, in the picture memory 101, a process for reordering imagedata of pictures which are inputted in the display order, to be arrangedin the picture coding order is carried out on the basis of therelationship between the target picture and a picture to be referred to,i.e., reference picture at the prediction coding. The picture memory 101outputs information indicating the size of an input image, i.e., inputimage size information Ipx, and this input image size information Ipx iscomposed of vertical pixel number information Ihpx indicating the number(h) of vertical pixels in the input image and horizontal pixel numberinformation Iwpx indicating the number (w) of horizontal pixels in theinput image.

[0154] The moving picture coding apparatus 10 a includes a predictionresidual decoder 104 that decompressively decodes output coded data Cdfrom the prediction residual encoder 102, and outputs differential dataof the target block (hereinafter, referred to as decoded differentialdata) PDd; an adder 106 that adds the decoded differential data PDd ofthe target data and the predictive data Pd of the target block, andoutputs image data of the target block (hereinafter, referred to asdecoded data) Rd; and a picture memory 105 that stores the decoded dataRd and outputs the stored decoded data Rd as data CRd of a candidate forpicture to be referred to at the coding of the target block, i.e.,reference candidate picture, in accordance with a picture designationsignal CSpd.

[0155] The moving picture coding apparatus 10 a includes a motionestimation unit 106 that estimates a motion vector MV for the targetblock on the basis of the output data, i.e., image data of the targetblock SId from the picture memory 101 and the output data, i.e., data ofa reference candidate picture CRd from the picture memory 105, andgenerates predictive data Pd for the target block on the basis of theestimated motion vector MV; and a motion vector storage unit 107 thatstores the motion vector MV for the target block, which has beenestimated by the motion vector estimation unit 106. The motionestimation unit 106 performs the motion estimation for estimating amotion vector for target block, with referring to an optimal pictureamong plural reference candidate pictures as well as referring to motionvectors for processed blocks that are located around the target block.Here, the optimal picture among the plural reference candidate picturesis decided on the basis of the coding efficiency or the like.

[0156] The moving picture coding apparatus 10 a includes a selectorswitch 111 that selects one of the output data SId from the picturememory 101 and the output data Dd from the difference calculator 113 andoutputs selected data CEd, and an ON/OFF switch 112 that is providedbetween the motion vector estimation unit 106 and the adder 114. Here,the selector switch 111 has two input terminals Ta1 and Ta2 and oneoutput terminal Tb, and the output terminal Tb is connected to one ofthe two input terminals Ta1 and Ta2 in accordance with a switch controlsignal.

[0157] The moving picture coding apparatus 10 a according to the firstembodiment includes a level analyzer 100 a that outputs informationindicating the maximum intra frame pixel number that can be coded (Nfpx)(hereinafter, referred to as maximum intra frame pixel numberinformation) Ifpx and information indicating the maximum storage pixelnumber which can be stored in a picture memory of a decoding apparatus(Nspx) (hereinafter, referred to as maximum storage pixel numberinformation) Ispx, on the basis of a level identifier signal indicatinga coding level, i.e., level signal Lst, which is inputted by a useroperation. This level analyzer 100 a has information of a table T1 asshown in FIG. 15. The table T1 shows correspondence between values ofthe level identifier, and the maximum intra frame pixel numbers and themaximum storage pixel numbers.

[0158] The moving picture coding apparatus 10 a includes a judgementunit, i.e., coding capability judgment unit 108 a that judges whethercoding of an input image is possible or not on the basis of the maximumintra frame pixel number information Ifpx from the level analyzer 100 aand input picture size information Ipx from the picture memory 101, andoutputs a signal indicating the judgment result, i.e., judgment resultsignal CSjd. The moving picture coding apparatus 10 a includes acalculator, i.e., maximum reference picture number calculator 109 a thatcalculates the number of reference candidate pictures, i.e., maximumreference picture number Nrpn which can be referred to at the interpicture prediction coding on the basis of the maximum storage pixelnumber information Ispx and the input image size information Ipx, andoutputs information, i.e., maximum reference picture number informationIrpn indicating the calculated number Nrpn.

[0159] The moving picture coding apparatus 10 a further includes a bitstream generator 103 that variable-length-codes the output coded data Cdfrom the prediction residual encoder 102, then adds codes correspondingto the motion vector MV, a mode signal Ms, and the level signal Lst to abit stream obtained by the variable length coding, and outputs anobtained bit stream Bsa.

[0160] The moving picture coding apparatus 10 a further includes acontrol unit 110 that controls operations of the respective componentsof the moving picture coding apparatus 10 a, in accordance with controlsignals Sct1, Sct2, . . . , Sctn, on the basis of the judgement resultsignal CSjd and the image data SId from the picture memory 101. Thecontrol unit 110 decides a coding mode according to the image data SIdfrom the picture memory 101, and outputs a mode signal Ms indicating thedecided mode, as well as controls the switches 111 and 112 according tothe decided coding mode, by predetermined signals. The control unit 110further controls operations of the prediction residual encoder 102, theprediction residual decoder 104, the bit stream generator 103, themotion vector estimation unit 106, and the like, in accordance with thecontrol signals Sct1, Sct2, . . . , Sctn, according to the judgmentresult signal CSjd. That is, the control unit 110 controls theprediction residual encoder 102, the prediction residual decoder 104,the bit stream generator 103, the motion vector estimation unit 106, andthe like, for performing coding of an input image when the judgmentresult signal CSjd indicates that it is possible to encode the inputimage, while controls the prediction residual encoder 102, theprediction residual decoder 104, the bit stream generator 103, themotion vector estimation unit 106, and the like, for not performingcoding of an input image when the judgment result signal CSjd indicatesthat it is impossible to encode the input image.

[0161]FIG. 14(a) shows a data structure of a bit stream Bsacorresponding to an input image.

[0162] The bit stream Bsa is composed of a header area Ha that containsvarious header information, and a sequence data part Dsq that containscoded data, i.e., a bit stream corresponding to image data of eachpicture.

[0163] A code H1 corresponding to the level identifier signal, i.e.,level signal Lst is included in the header area Ha of the bit streamBsa, as one kind of the header information. Further, a sequence headerSh indicating the size of an input image, i.e., the number of verticalpixels in the input image (hereinafter, referred to as input imagevertical pixel number) (h) and the number of horizontal pixels in theinput image (hereinafter, referred to as input image horizontal pixelnumber) (w) is included in the sequence data part Dsp of the bit streamBsa.

[0164]FIG. 2 is a diagram illustrating a specific construction of thecoding capability judgment unit 108 a.

[0165] The coding capability judgment unit 108 a includes a multiplier206 that calculates the product (Phw) of the input image vertical pixelnumber (h) and the input image horizontal pixel number (w) on the basisof the input pixel vertical pixel number information Ihpx and the inputpixel horizontal pixel number information Iwpx, and outputs amultiplication signal Shw indicating the result of the multiplication;and a first comparator 203 that compares the product (Phw) and themaximum intra frame pixel number Nfpx on the basis of the multiplicationsignal Shw and the maximum intra frame pixel number information Ifpx,and outputs a first comparison result signal Scm1 indicating the resultof comparison.

[0166] The coding capability judgment unit 108 a includes a calculator,i.e., maximum vertical pixel number/maximum horizontal pixel numbercalculator 201 that calculates the maximum vertical pixel number (H) andthe maximum horizontal pixel number (W) which can be processed, on thebasis of the input image vertical pixel number information Ihpx and theinput image horizontal pixel number information Iwpx, and outputsinformation Op3 a and Op3 b indicating the operation results; and a16-multiple converter 202 that performs a rounding operation forrounding the maximum vertical pixel number (H) and the maximumhorizontal pixel number (W) to multiples of 16 on the basis of theoperation result information Op3 a and Op3 b from the calculator 201,and outputs rounding information Trnd1 indicating a multiple of 16 towhich the maximum vertical pixel number (H) is rounded (round1(H)) androunding information Trnd2 indicating a multiple of 16 to which themaximum horizontal pixel number (W) is rounded (round2(H)).

[0167] The coding capability judgment unit 108 a includes a secondcomparator 204 that performs comparison between the input image verticalpixel number (h) and the maximum vertical pixel number (H) (verticalpixel number comparison) and comparison between the input imagehorizontal pixel number (w) and the maximum horizontal pixel number (W)(horizontal pixel number comparison) on the basis of the pixel numberinformation Ihpx and Iwpx, and the rounding information Trnd1 and Trnd2,and outputs a comparison result signal Scm2 a indicating the result ofthe vertical pixel number comparison, and a comparison result signalScm2 b indicating the result of the horizontal pixel number comparison;and an AND unit 205 that takes an AND operation of the three comparisonresult signals Scm1, Scm2 a and Scm2 b, and outputs the operation resultsignal CSjd indicating the result of AND operation.

[0168]FIG. 3 is a diagram illustrating a specific construction of themaximum reference picture number calculator 109 a.

[0169] The maximum reference picture number calculator 109 a includes amultiplier 401 that calculates the total number of pixels in one frame(Phw=h×w) corresponding to the size of the input image on the basis ofthe input image vertical pixel number information Ihpx and the inputimage horizontal pixel number information Iwpx, and outputs an operationoutput Ohw indicating the result of calculation; and a divider 402 thatdivides the maximum storage pixel number (Nspx) by the total pixelnumber in one frame (h×w) on the basis of the operation output Ohw andthe maximum storage pixel number information Ispx, and outputs anoperation output signal Dpm indicating the result of division(Nspx/(h×w)). The maximum reference picture number calculator 109 afurther includes a constant storage unit 404 that retains a numericvalue signal Sn1 indicating the number of pictures to be coded, i.e.,one picture, and outputs the numeric value signal Sn1; and a subtractor403 that outputs a subtraction output signal Sd1 indicating a valueobtained by subtracting 1 from the division result (Nspx/(h×w) i.e.,Nspx/(h×w)−1.

[0170] Next, the operation will be described hereinafter.

[0171] In the moving picture coding apparatus 10 a according to thefirst embodiment, before performing a coding of an input image, a levelrequired is selected from a plurality of coding levels which arepreviously established and are employed as coding conditions, on thebasis of the construction of a memory or the like in the moving picturecoding apparatus 10 a, and the construction of a memory or the like in amoving picture decoding apparatus to which coded data are supplied. Morespecifically, the coding level selection is performed by the user withreferring to the table T1, and the level signal Lst indicating the levelidentifier corresponding to the selected level is inputted to the movingpicture coding apparatus 10 a by the user operation.

[0172] In this case, a specific maximum intra frame pixel number (Nfpx)and maximum storage pixel number (Nspx) are set for each coding level.The table T1 in FIG. 15 shows eight coding levels, which correspond tovalues (1) to (8) of the level identifier, respectively. Further, thevalues (1) to (8) of the level identifier are correlated with specificvalues of the maximum intra frame pixel number (Nfpx) and specificvalues of the maximum storage pixel number (Nspx), respectively.

[0173] The maximum intra frame pixel number (Nfpx) indicates the size ofa picture constituting an input image, i.e., input moving picture, whichcan be coded by the moving picture coding apparatus 10 a and can decodedby a moving picture decoding apparatus to which the coded data aresupplied, and this is the maximum value possibly taken by the product ofthe number of vertical pixels (h) and the number of horizontal pixels(w) in the picture. More specifically, the maximum intra frame pixelnumber indicates the maximum value of the number of pixels per picture.

[0174] The maximum storage pixel number (Nspx) indicates the number ofpixels corresponding to the amount of image data which can be stored ina picture memory in a decoding apparatus associated with the movingpicture coding apparatus 10 a. In other words, the maximum storage pixelnumber (Nspx) is the number of pixels equivalent to the maximum amountof image data which can be stored in the picture memory. For example,data of pictures such as reference candidate pictures, decoded picturesthat wait for being displayed, and a picture to be decoded are stored inthe picture memory of the moving picture decoding apparatus that decodesa bit stream from the moving picture coding apparatus 10, and themaximum storage pixel number is equal to the total number of the pixelsin these pictures.

[0175] In this moving picture coding apparatus 10 a, when the selectionof the coding level is performed by the user operation, the levelselection signal Lst is inputted to the level analyzer 100 a. Then, thelevel analyzer 10 a refers to the table T1 (see FIG. 15) held therein,and outputs the maximum intra frame pixel number information Ifpx andthe maximum storage pixel number information Ispx adaptively to thecoding level indicated by the level signal Lst, which is selected by theuser. The maximum intra frame pixel number information Ifpx is inputtedto the coding capability judgment unit 108 a, and the maximum storagepixel number information Ispx is inputted to the maximum referencepicture number calculator 109 a.

[0176] When image data Id of a moving picture, i.e., input image isinputted to the picture memory 101 in picture units in the order ofdisplay time, image data corresponding to each picture is successivelystored in the picture memory 101, and the stored image data SId isoutputted from the picture memory 101 in units of blocks, i.e.,macroblocks that constitute the picture, in the order of coding. At thistime, the information indicating the size of the input image, i.e.,input image size information Ipx is outputted from the picture memory101 to the coding capability judgment unit 108 a and the maximumreference picture number calculator 109 a.

[0177] Here, for example, the macroblock is a block in which the numberof horizontal pixels (hereinafter, referred to as horizontal pixelnumber) is 16, and the number of vertical pixels (hereinafter, referredto as vertical pixel number) is 16 (16×16 pixel block). Then, the codingprocess in the moving picture coding apparatus is performed in units ofblocks. Further, as described above, the input image size informationIpx is composed of the information Ihpx indicating the number ofvertical pixels (h) in the input image and the information Iwpxindicating the number of horizontal pixels (w) in the input image.

[0178] Then, the coding capability judgment unit 108 a judges whetherthe input image is encodable on the basis of the vertical pixel numberinformation Ihpx and the horizontal pixel number information Iwpx of theinput image included in the input image size information Ipx, which isoutputted from the picture memory 101, and the maximum intra frame pixelnumber information Ifpx outputted from the level analyzer 10 a, andoutputs a signal indicating the judgment result, i.e., judgment resultsignal CSjd to the control unit 110.

[0179] The control unit 110 controls the respective units in the movingpicture coding apparatus 10 a for performing coding of the image dataSId from the picture -memory 101 in accordance with control signalsSct1, Sct2, . . . , Sctn, when the judgment result signal CSjd indicatesthat the input image is encodable, while controlling the respectiveunits in the moving picture coding apparatus 10 a for not performingcoding of the image data SId from the picture memory 101 in accordancewith the control signals Sct1, Sct2, . . . , Sctn, when the judgementresult signal CSjd indicates that it is impossible to code the inputimage.

[0180] Further, the control unit 110 switches between a mode forperforming inter picture prediction coding for image data and a mode forperforming intra picture prediction coding for image data, on the basisof the image data SId from the picture memory 101, when the judgmentresult signal CSjd indicates that the input image is encodable. When thecontrol unit 110 selects the mode for performing the inter pictureprediction coding of image data, it controls the switch 111 so that theoutput terminal Tb is connected to the second input terminal Ta2, andcontrols the switch 112 so as to be brought into conduction, by apredetermined control signal. On the other hand, when the control unit110 selects a mode for performing inter picture prediction coding ofimage data, the control unit 110 controls the switch 111 so that theoutput terminal Tb is connected to the first input terminal Ta1, andcontrols the switch 112 so as to be brought out of conduction, by apredetermined control signal.

[0181] The maximum reference picture number calculator 109 a calculatesthe number of reference candidate pictures which can be referred to atthe inter picture prediction coding (hereinafter, referred to as amaximum reference picture number) (Nrpn), on the basis of the maximumstorage pixel number information Ispx, the input image vertical pixelnumber information Ihpx, and the input image horizontal pixel numberinformation Iwpx, and outputs information indicating the calculatednumber (Nrpn), i.e., reference picture maximum number Irpn.

[0182] Hereinafter, the operation in a case where the inter pictureprediction coding is selected will be described.

[0183] The image data SId of a macroblock, which has been read from thepicture memory 101 is input to the motion vector estimation unit 106. Atthis time, decoded image data Rd corresponding to coded pictures arestored in the picture memory 105 as image data of reference candidatepictures, and a required picture among the reference candidate picturesin the picture memory 105 is designated as a reference picture by thepicture designation signal CSpd from the motion vector estimation unit106. The motion vector estimation unit 106 employs image data of thedesignated reference candidate picture as image data CRd of thereference picture, to perform a process for estimating a motion vectorMV for the target macroblock to be coded. Image data of a referenceimage corresponding to the target macroblock, which is decided by theobtained motion vector MV is inputted to the difference calculator 113as predictive data Pd for the target macroblock.

[0184] The difference calculator 113 calculates a difference between theimage data SId of the target macroblock and the predictive data Pd togenerate prediction residual image data Dd, and then the predictionresidual encoder 102 encodes the prediction residual image data Dd andoutputs prediction residual coded data Cd.

[0185] Then, the prediction residual decoder 104 decodes the predictionresidual coded data Cd, and outputs prediction residual image data PDdobtained by the decoding, to the adder 114. The adder 114 adds theprediction residual image data PDd from the prediction residual decoder104 and the predictive data Pd from the motion vector estimation unit106, and then the image data Rd obtained by the addition is stored inthe picture memory 105.

[0186] The bit stream generator 103 generates a bit stream correspondingto the prediction residual coded data Cd that is outputted from theprediction residual encoder 102, and outputs the generated bit streamtogether with a code corresponding to the motion vector MV from themotion vector estimation unit 106, a code corresponding to a mode signalMs from the control unit 110, and a code corresponding to the levelsignal Lst, as a bit stream Bsa. As shown in FIG. 14(a), the code H1corresponding to the level signal Lst is included in the header area Haof the bit stream Bsa, and the image information that is generated bythe coding in units of macroblocks, the code corresponding to the motionvector, and the code corresponding to the mode signal are included inthe sequence data part Dsp, together with the sequence header Sh. Thesequence header Sh includes a code corresponding to the information Ipxthat indicates the number of vertical pixels (h) and the number ofhorizontal pixels (2) of the input image.

[0187] Next, the operation in a case where intra picture predictioncoding is selected will be briefly described.

[0188] In this case, the image data SId outputted from the picturememory 101 is inputted to the prediction residual encoder 102 throughthe switch 111, and then encoded by the encoder 102 to be inputted tothe bit stream generator 103.

[0189] The bit stream generator 103 generates a bit stream correspondingto the coded data Cd outputted from the encoder 102, and outputs thegenerated bit stream together with the code corresponding to the modesignal Ms from the control unit 110 and the code corresponding to thelevel signal Lst, as a bit stream Bsa (see FIG. 14(a)).

[0190] The prediction residual decoder 104 decodes the coded data Cdoutputted from the prediction residual encoder 102, and stores theprediction residual image data PDd obtained by the decoding in thepicture memory 105 through the adder 114 as it is, as the image data Rd.

[0191] Next, a specific operation of the coding capability judgment unit108 a in the moving picture coding apparatus 10 a will be described withreference to FIG. 2.

[0192] The coding capability judgment unit 108 a in the moving picturecoding apparatus 10 a according to the first embodiment judges thecapability of coding for an input image in accordance with followingconditional formulae: (formula 1), (formula 2a), (formula 2b), (formula3a), and (formula 3b). The conditional formulae: (formula 1), (formula2a), and (formula 2b) are defined by claim 3, and the conditionalformulae: (formula 3a) and (formula 3b) are defined by claim 7.

h×w<=Nfpx  (formula 1)

h<=round1(H)  (formula 2a)

w<=round2(W)  (formula 2b)

H=sqrt(h×w×N)  (formula 3a)

W=sqrt(h×w×N)  (formula 3b)

[0193] Here, Nfpx designates the maximum intra frame pixel number, hdesignates the number of vertical pixels in a target picture to becoded, w designates the number of horizontal pixels in the targetpicture, H designates the maximum number of vertical pixels of an inputimage, which can be coded by the moving picture coding apparatus 10 a, Wdesignates the maximum number of horizontal pixels of an input image,which can be coded by the moving picture coding apparatus 10 a, and Ndesignates an arbitrary natural number. Further, round1( ) is a signthat designates the result of an operation for rounding the value of anargument in parentheses to a multiple of the vertical pixel number in amacroblock, i.e., the unit of coding, round2( ) is a sign thatdesignates the result of an operation for rounding the value of anargument in parentheses to a multiple of the horizontal pixel number inthe macroblock, i.e., the unit of coding, sqrt( ) is a sign thatdesignates the square root of an argument in parentheses.

[0194] Initially, the coding capability judgment unit 108 a performs theoperation indicated by (formula 1) on the basis of the vertical pixelnumber information Ihpx and the horizontal pixel number information Iwpsof the input image included in the input image size information Ipx thatis outputted from the picture memory 101. More specifically,multiplication for obtaining the product (h×w) of the vertical pixelnumber (h) and the horizontal pixel number (w) in the input image iscarried out by the multiplier 206, and further comparison between themultiplication result (h×w) and the maximum intra frame pixel number(Nfpx) is performed by the first comparator 203 on the basis of a signalShw indicating the result of the multiplication and the maximum intraframe pixel number information Ifpx. The comparison result signal Scm1indicating the result of the comparison is outputted from the firstcomparator 203 to the AND unit 205.

[0195] Next, in the coding capability judgment unit 108 a, the maximumvertical pixel number/maximum horizontal pixel number calculator 201calculates the maximum number of vertical pixels (H) and the maximumnumber of horizontal pixels (W) indicated by (formula 3a) and (formula3b) on the basis of the vertical pixel number information Ihpx and thehorizontal pixel number information Iwpx for the input image.

[0196] Here, (formula 3a) and (formula 3b) show that the maximumvertical pixel number (H) and the maximum horizontal pixel number (W)are both a positive square root of a value that is obtained bymultiplying the product of the vertical pixel number (h) and thehorizontal pixel number (w) of the input image, by N. For example, whenN=8, (formula 3a) suggests that the maximum vertical pixel number (H) isdecided so that the ratio between the vertical pixel number and thehorizontal pixel number is less than 8:1, and (formula 3b) suggests thatthe maximum horizontal pixel number (W) is decided so that the ratiobetween the vertical pixel number and the horizontal pixel number isless than 1:8.

[0197] The operation result signals Op3 a and Op3 b indicating themaximum vertical pixel number (H) and the maximum horizontal pixelnumber (W) which are obtained by the maximum vertical pixelnumber/maximum horizontal pixel number calculator 201 are inputted tothe 16-mulitple converter 202, and the 16-multiple converter 202 roundsthe maximum vertical pixel number (H) and the maximum horizontal pixelnumber (W) to a multiple of 16, respectively, by an operation, such asomission, raising, or half-adjust. The 16-mulitple converter 202 outputsrounding operation information Trnd1 indicating a value, i.e., round1(H)that is obtained by rounding the maximum vertical pixel number (H) to amultiple of 16, and rounding operation information Trnd2 indicating avalue (round2(H)) that is obtained by rounding the maximum horizontalpixel number (W) to a multiple of 16, to the second comparator 204.Further, the second comparator 204 performs comparison between the inputimage vertical pixel number (h) and the maximum vertical pixel number(H) (hereinafter, referred to as vertical pixel number comparison) andcomparison between the input image horizontal pixel number (w) and themaximum horizontal pixel number (W) (hereinafter, referred to ashorizontal pixel number comparison), on the basis of the pixel numberinformation Ihpx and Iwpx and the rounding operation information Trnd1and Trnd2, and outputs the comparison result signal Scm2 a indicatingthe result of the vertical pixel number comparison and the comparisonresult signal Scm2 b indicating the result of the horizontal pixelnumber comparison to the AND unit 205.

[0198] In this first embodiment, the rounding operation for the maximumvertical pixel number (H) and the maximum horizontal pixel number (W) bythe 16-mulitple converter 202 is a processing of rounding these pixelnumbers to multiples of 16. However, the value “16” in the roundingoperation corresponds to the number of pixels that constitute one sideof a macroblock as the unit for coding, and thus in a case where thenumber of pixels that constitute one side of a macroblock is not 16, therounding operation rounds the maximum vertical pixel number and themaximum horizontal pixel number to multiples of a value corresponding tothe number of pixels that constitute one side of a macroblock, which isa value other than 16, is performed. When the rounding operation roundsthe maximum vertical pixel number and the maximum horizontal pixelnumber to multiples of a value corresponding to the number of pixelsthat constitute one side of a macroblock, i.e., a value other than 16,the number of macroblocks in a frame corresponding to an input imagethat can be coded, or the number of macroblocks in the horizontal orvertical direction with respect to the frame is uniquely decided,whereby mapping of image data in the picture memory or the like can beperformed efficiently.

[0199] Then, the AND unit 205 takes an AND of the comparison resultsignal Scm1 outputted from the first comparator 203 and the comparisonresult signals Scm2 a and Scm2 b outputted from the second comparator204, and outputs a signal, i.e., judgment result signal CSjd indicatinga final result of the judgment as to coding capability.

[0200] Next, a specific operation of the maximum reference picturenumber calculator 109 a in the moving picture coding apparatus 10 a willbe described with reference to FIG. 3.

[0201] The maximum reference picture number calculator 109 a in themoving picture coding apparatus 10 a according to the first embodimentcalculates the maximum number of reference candidate pictures to beemployed at inter picture prediction coding on the basis of an operationshown by following (formula 4). Here, (formula 4) is defined by claim 5.

Nrpn=Nspx÷(h×w)−1  (formula 4)

[0202] Here, h denotes the number of vertical pixels in an input image,i.e., target picture to be coded, and w denotes the number of horizontalpixels in the input image, i.e., target picture to be coded. Nrpndenotes the maximum number of reference pictures, and Nspx denotes themaximum number of storage pixels. In this first embodiment, the maximumstorage pixel number Nspx is the maximum value for the total numbers ofpixels in reference pictures and a target picture to be decoded, whoseimage data are stored in a picture memory of a moving picture decodingapparatus that decodes the bit stream Bsa outputted from the movingpicture coding apparatus 10 a.

[0203] The maximum reference picture number calculator 109 a calculatesthe total number of pixels (h×w) in one frame, as the size of the inputimage, on the basis of the input image vertical pixel number informationIhpx and the input image horizontal pixel number information Iwpx. Thatis, the multiplier 401 multiplies the number of vertical pixels in theinput image (h), which is indicated by the input image vertical pixelnumber information Ihpx, by the number of horizontal pixels (w)indicated by the input image horizontal pixel number information Iwpx,and outputs an operation output Ohw indicating the multiplication result(h×w).

[0204] Further, the divider 402 divides the maximum storage pixel number(Nspx) by the multiplication result (h×w) on the basis of the operationoutput Ohw from the multiplier 401 and the maximum storage pixel numberinformation Ispx from the level analyzer 100 a, and outputs an operationoutput signal Dpm indicating the result of division (Nspx/(h×w)).

[0205] The subtractor 403 subtracts 1 from the division result(Nspx/(h×w)) on the basis of the operation output signal Dpn from thedivider 402 and the numeric value information Sn1 from the constantstorage unit 404, and outputs a subtraction output signal Sd1 indicatingthe result of subtraction (Nspx/(h×w)−1).

[0206] The reason why the subtractor 403 subtracts 1 from the divisionresult (Nspx/(h×w)) is that decoded image data of a picture to bedecoded must be stored in a picture memory of the decoding apparatus, inaddition to the image data of reference candidate pictures which areemployed at the inter picture prediction coding in the decodingapparatus.

[0207] As described above, the moving picture coding apparatus 10 aaccording to the first embodiment includes the level analyzer 10 a thatdecides the maximum number of intra frame pixels (Nfpx) which can becoded and the maximum number of storage pixels (Nspx) which can bestored in the picture memory of the decoding apparatus, on the basis ofthe level signal Lst indicating a coding level that is designated by theuser, thereby judging whether the input image is encodable or not, onthe basis of the maximum intra frame pixel number (Nfpx) and the inputimage size, i.e., the vertical pixel number Nhpx and the horizontalpixel number Nwpx, and calculating the number of reference candidatepictures, i.e., reference picture maximum number Nrpn which can bereferred to at the inter picture prediction coding. Therefore, adecoding apparatus to which a bit stream from the moving picture codingapparatus 10 a is supplied can always decode the bit streamsatisfactorily, thereby performing inter picture prediction decodingcorresponding to the inter picture prediction coding on the coding end.Accordingly, it is possible to design the memory areas in the codingapparatus as well as in the decoding apparatus which are compliant witha coding method which has no restraint on the capacity of the memoryarea.

[0208] In this first embodiment, as a table that defines thecorrespondence between the plural coding levels, i.e., values of thelevel identifier, and the maximum intra frame pixel number and themaximum storage pixel number, the table T1 in which the coding levels,i.e., values of the level identifier are correlated with pairs of themaximum intra frame pixel number and the maximum storage pixel number(see FIG. 15) is employed. However, a table T1 a in which values of thelevel identifier are correlated with the maximum intra frame pixelnumbers (FIG. 16(a)) and a table T1 b in which values of the levelidentifier are correlated with the maximum storage pixel numbers (FIG.16(b)) may be employed.

[0209] Further, in this first embodiment, the decision of the codinglevel, i.e., value of the level identifier by the user is performed withreference to the Table T1 shown in FIG. 15, while the decision of thecoding level by the user may be performed by utilizing following(formula 5), in place of the table T1 shown in FIG. 15.

(Level identifier value)=transA (maximum intra frame pixel number,maximum storage pixel number)  (formula 5)

[0210] Here, transA( ) is a sign that indicates an operation of giving avalue of the level identifier, using the maximum intra frame pixelnumber and the maximum storage pixel number as arguments. According to(formula 5), when the user designates the maximum intra frame pixelnumber and the maximum storage pixel number of the input image to becoded by the moving picture coding apparatus 10 a, the correspondingvalue of the level identifier is decided.

[0211] Further, following (formula 6a) and (formula 6b) may be employedin place of the table T1 a indicating the correspondence between thelevel identifier value and the maximum intra frame pixel number (FIG.16(a)) and the table T1 b indicating the correspondence between thelevel identifier value and the maximum storage pixel number (FIG.16(b)).

(Level identifier value)=transAa (the maximum intra frame pixelnumber)  (formula 6a)

(Level identifier value)=transAb (the maximum storage pixelnumber)  (formula 6b)

[0212] Here, transAa ( ) is a sign indicating an operation for giving avalue of the level identifier, using the maximum intra frame pixelnumber as an argument. According to (formula 6a), when the userdesignates the maximum intra frame pixel number of the input image whichcan be coded by the moving picture coding apparatus, the correspondingvalue of the level identifier is decided.

[0213] Further, transAb ( ) is a sign indicating an operation for givinga value of the level identifier, using the maximum storage pixel numberas an argument. According to (formula 6b), when the user designates themaximum storage pixel number of the input image which can be coded bythe moving picture coding apparatus, the corresponding value of thelevel identifier is decided.

[0214] According to the moving picture coding apparatus of the firstembodiment, the maximum storage pixel number is a total number of pixelsin pictures, corresponding to the highest amount of image data that canbe stored in the picture memory of the decoding apparatus to which a bitstream is supplied. However, in place of the maximum storage pixelnumber, the memory capacity itself, which is required by the picturememory of the decoding apparatus may be employed.

[0215] In this first embodiment, the maximum storage pixel number Nspxis the maximum value of the total number of pixels in all storagepictures whose image data are stored in the picture memory of the movingpicture decoding apparatus that decodes a bit stream that is obtainedfrom the moving picture coding apparatus 10 a. The description has beengiven, taking the case where the reference pictures and the targetpicture to be decoded are the storage pictures as an example, but themaximum storage pixel number may be defined not to include the number ofpixels in the target picture to be decoded.

[0216] In this case, following (formula 7a) is employed in place ofabove (formula 4).

Nrpn=Nspx÷(h×w)  (formula 7a)

[0217] Here, h denotes the number of vertical pixels in a target pictureto be coded, w denotes the number of horizontal pixels in the targetpicture, Nrpn denotes the maximum number of reference pictures, and Nspxdenotes the maximum number of stored pixels.

[0218] In the maximum reference picture number calculator 109 a shown inFIG. 3, the maximum reference picture number is decided withoutexecuting the process of subtracting 1 from the division result(Nspx/(h×w)).

[0219] [Embodiment 2]

[0220]FIG. 4 is a block diagram for explaining a moving picture codingapparatus 10 b according to a second embodiment of the presentinvention.

[0221] The moving picture coding apparatus 10 b according to the secondembodiment has, in place of the level analyzer 100 a and the codingcapability judgment unit 108 a of the moving picture coding apparatus 10a of the first embodiment, a level analyzer 100 b that outputs pixelnumber calculation coefficient information αpx, as well as the maximumintra frame pixel number Ifpx and the maximum storage pixel numberinformation Ispx, on the basis of the level signal Lst and anidentification number signal Cid which are inputted; and a codingcapability judgment unit 108 b that judges whether the input image isencodable or not on the basis of the maximum intra frame pixel numberinformation Ifpx, the pixel number calculation coefficient information apx, and the input image size information Ipx. Here, the identificationnumber Cid indicates a value of the identification number decided underthe control by the user, and this identification number is employed toidentify a specific value of the pixel number calculation coefficient asan additional coding condition. The level analyzer 100 b includesinformation of the table T1 shown in FIG. 15 and a table T2 shown inFIG. 17(a). The table T1 shows correspondence between the value of thelevel identifier, and the maximum intra frame pixel number and themaximum storage pixel number. The table T2 shows correspondence betweenthe value of the identification number, and the vertical pixel numbercalculation coefficient (Nαhpx) and the horizontal pixel detectioncoefficient (Nαwpx). Further, pixel number calculation coefficientinformation α px is composed of information indicating the verticalpixel number calculation coefficient (Nαhpx) (hereinafter, referred toas vertical pixel number calculation coefficient information) αhpx andinformation indicating the horizontal pixel number calculationcoefficient (Nαwps) (hereinafter, referred to as horizontal pixel numbercalculation coefficient information) αwpx. The bit stream generator 103of the moving picture coding apparatus 10 b subjects output data, i.e.,coded data Cd from the prediction residual coding unit 102 to variablelength coding, and outputs a bit stream Bsb that is obtained by addingcodes corresponding to the motion vector MV, the mode signal Ms, thelevel signal Lst, and the identification number signal Cid, to the bitstream obtained by the variable length coding.

[0222] The constructions of the components other than the moving picturecoding apparatus 10 b according to the second embodiment are the same asthose of the moving picture coding apparatus 10 a according to the firstembodiment.

[0223]FIG. 14(b) shows a data structure of a bit stream Bsbcorresponding to an input image.

[0224] The bit stream Bsb is composed of a header area Hb that containsvarious kinds of header information, and a sequence data part Dsq thatcontains coded data, i.e., bit stream corresponding to image data ofeach picture.

[0225] In the header area Hb of the bit stream Bsb, a code H1corresponding to a signal of the level identifier, i.e., level signalLst and a code H2 corresponding to the identification number signal Cidare included as the header information. Further, in the sequence datapart Dsq of the bit stream Bsb, a sequence header Sh indicating the sizeof the input image, i.e., the input image vertical pixel number (h) andthe input image horizontal pixel number (w) is included. To be morespecific, the code H2 is obtained by coding the identification numbersignal Cid that indicates the value of the identification number foridentifying the vertical pixel number calculation coefficient (Nαhpx)and the horizontal pixel number calculation coefficient (Nαwpx), asshown in FIG. 17(a).

[0226]FIG. 5 is a diagram illustrating a specific construction of thecoding capability judgment unit 108 b.

[0227] This coding capability judgment unit 108 b has, in place of themaximum vertical pixel number/maximum horizontal pixel number calculator201 of the coding capability judgment unit 108 a according to the firstembodiment, a calculator, i.e., maximum vertical pixel number/maximumhorizontal pixel number calculator 301 that calculates the maximumnumber of vertical pixels (H) and the maximum number of horizontalpixels (W) which can be processed, on the basis of the maximum intraframe pixel number information Ifpx, the vertical pixel numbercalculation coefficient information αhpx, and the horizontal pixelnumber calculation coefficient information αwpx, and outputs informationOp3 a and Op3 b indicating the calculation results. Therefore, themultiplier 306, the first comparator 303, the second comparator 304, the16-mulitple converter 302, and the AND unit 305 in the coding capabilityjudgment unit 108 b are the same as the multiplier 208, the firstcomparator 203, the second comparator 204, the 16-mulitple converter202, and the AND unit 205 in the coding capability judgment unit 108 aaccording to the first embodiment.

[0228] Next, the operation will be described.

[0229] The operation of the moving picture coding apparatus 10 baccording to the second embodiment is different from that of the movingpicture coding apparatus 10 a according to the first embodiment only inthe operations of the level analyzer 100 b, the coding capabilityjudgment unit 108 b, and the bit stream generator 103.

[0230] Thus, the operations of the level analyzer 100 b, the codingcapability judgment unit 108 b, and the bit stream generator 103 will bemainly described hereinafter.

[0231] For the moving picture coding apparatus 10 b of the secondembodiment, before the coding for an input image is performed, arequired level is selected from among plural preset coding levels whichare employed as coding conditions, on the basis of the construction ofthe memory and the like in the moving picture coding apparatus 10 b, andthe construction of a memory and the like in a moving picture decodingapparatus to which coded data are to be supplied, and further a requiredlevel of plural identification numbers, which are employed as additionalcoding conditions is selected. More specifically, the selection of thecoding level is performed by the user with referring to the table T1,and the level signal Lst indicating the level identifier correspondingto the selected level is inputted to the moving picture coding apparatus10 b by the user operation. Further, the selection of the level of theidentification number is performed by the user with referring to thetable T2, and the identification number signal Cid indicating theidentification number corresponding to the selected level is inputted tothe moving picture coding apparatus 10 b by the user operation.

[0232] Here, the coding level, the maximum intra frame pixel number, andthe maximum storage pixel number are the same as those in the firstembodiment. The table T2 shown in FIG. 17(a) sets four levels of theidentification number, and the respective levels of the identificationnumber correspond to values (1)-(4) of the identification numbers,respectively. The values (1)-(4) of the identification number arecorrelated with specific values of the vertical pixel number calculationcoefficient (Nαhpx), and specific values of the horizontal pixel numbercalculation coefficient (Nαwpx), respectively.

[0233] According to the moving picture coding apparatus 10 b, when thelevel signal Lst and the identification number signal Cid which areinputted under the control by the user are supplied to the levelanalyzer 100 b, the level analyzer 100 b refers to table T1 (FIG. 15)and table T2 (FIG. 17(a)) which are held therein, to output the maximumintra frame pixel number information Ifpx and the maximum storage pixelnumber information Ispx corresponding to the coding level indicated bythe level signal Lst, which has been selected by the user, and furtheroutput the pixel number calculation coefficient information αpxcorresponding to the level of the identification number indicated by theidentification number signal Cid, which has been selected by the user.The maximum intra frame pixel number information Ifpx and the pixelnumber calculation coefficient information αpx is inputted to the codingcapability judgment unit 108 b, and the maximum storage pixel numberinformation Ispx is inputted to the maximum reference picture numbercalculator 109 a.

[0234] When image data Id of a moving picture (input image) is inputtedto the picture memory 101 in units of pictures in the display order,image data corresponding to each picture is successively stored in thepicture memory 101, and the stored image data SId is outputted from thepicture memory 101 in units of blocks, i.e., macroblocks that constitutethe picture in the order of coding. At this time, information indicatingthe size of the input image, i.e., input image size information Ipx isoutputted from the picture memory 101 and inputted to the codingcapability judgment unit 108 b and the maximum reference picture numbercalculator 109 a.

[0235] Then, the coding capability judgment unit 108 b judges whetherthe input image is encodable or not on the basis of the input image sizeinformation Ipx from the picture memory 101, and the maximum intra framepixel number information Ifpx and the pixel number calculationcoefficient information α px from the level analyzer 100 b, and outputsa signal indicating the judgment result, i.e., judgment result signalCSjd to the control unit 110.

[0236] When the judgment result signal CSjd indicates that the inputimage is encodable, the control unit 110 switches between a mode forperforming inter picture prediction coding for image data and a mode forperforming intra picture prediction coding for image data, on the basisof the image data SId from the picture memory 101, and outputs controlsignals for respective units. The respective units of the moving picturecoding apparatus 10 b are controlled in accordance with the controlsignals Sct1, Sct2, . . . , Sctn corresponding to the judgment resultsignal CSjd, from the control unit 110, like in the first embodiment.

[0237] The maximum reference picture number calculator 109 a calculatesthe maximum number of reference pictures (Nrpn) on the basis of themaximum storage pixel number information Ispx, and the input imagevertical pixel number information Ihpx and horizontal pixel numberinformation Iwpx, and outputs information, i.e., reference picturemaximum number information Irpn indicating the calculated number (Nrpn).

[0238] In this second embodiment, when the inter picture predictioncoding mode is selected, the inter picture prediction coding for theinput image is performed in the same manner as in the first embodiment,and when the intra picture prediction coding is selected, the intrapicture prediction coding for the input image is performed in the samemanner as in the first embodiment.

[0239] In this second embodiment, however, when the inter pictureprediction coding mode is selected, the bit stream generator 103generates a bit stream corresponding to prediction residual coded dataCd that is outputted from the prediction residual encoder 102, andoutputs the generated bit stream together with a code corresponding tothe motion vector MV from the motion vector estimation unit 106, a codecorresponding to the mode signal Ms from the control unit 110, a codecorresponding to the level signal Lst, and a code corresponding to theidentification number signal Cid, as a bit stream Bsb (see FIG. 14(b)).When the intra picture prediction coding mode is selected, the bitstream generator 103 generates a bit stream corresponding to coded dataCd that is outputted from the encoder 102, and outputs the generated bitstream together with the code corresponding to the mode signal Ms fromthe control unit 110, the code corresponding to the level signal Lst,and the code corresponding to the identification number signal Cid, as abit stream Bsb (see FIG. 14(b)).

[0240] Next, a specific operation of the coding capability judgment unit108 b of the moving picture coding apparatus 10 b will be described withreference to FIG. 5.

[0241] In the coding capability judgment unit 108 b of the movingpicture coding apparatus 10 b according to the second embodiment, thecapability of the coding for an input image is judged on the basis ofthe following conditional formulae (formula 1), (formula 2a), (formula2b), (formula 8a), and (formula 8b). The conditional formulae (formula1), (formula 2a), and (formula 2b) are defined by claim 3, and theconditional formulae (formula 8a) and (formula 8b) are defined by claim9.

H=Nfpx÷Nαhpx  (formula 8a)

W=Nfpx÷Nαwpx  (formula 8b)

[0242] Here, Nfpx denotes the maximum number of intra frame pixels, Hdenotes the maximum number of vertical pixels in an input image, whichcan be coded by the moving picture coding apparatus 10 b, and W denotesthe maximum number of horizontal pixels in the input image, which can becoded by the moving picture coding apparatus 10 b. Nαhpx denotes avertical pixel number calculation coefficient, and Nαwpx denotes ahorizontal pixel number calculation coefficient.

[0243] Initially, like the coding capability judgment unit 108 aaccording to the first embodiment, the coding capability judgment unit108 b performs the operation indicated by (formula 1) on the basis ofthe input image vertical pixel number information Ihpx and horizontalpixel number information Iwpx included in the input image sizeinformation Ipx, which is outputted from the picture memory 101. Morespecifically, multiplication for obtaining the product (h×w) of thenumber of vertical pixels (h) and the number of horizontal pixels (w) inthe input image is carried out by the multiplier 306, and comparisonbetween the multiplication result (h×w) and the maximum intra framepixel number (Nfpx) is carried out by the first comparator 303. Thefirst comparator 303 outputs a comparison result signal Scm1 indicatingthe result of comparison to the AND unit 305.

[0244] Then, in the coding capability judgment unit 108 b, the maximumvertical pixel number/maximum horizontal pixel number calculator 301calculates the maximum number of vertical pixels (H) indicated by(formula 8a) and the maximum number of horizontal pixels indicated by(formula 8b) on the basis of the maximum intra frame pixel numberinformation Ifpx, the vertical pixel number calculation coefficientinformation a hpx, and the horizontal pixel number calculationcoefficient information αwps.

[0245] Here, (formula 8a) and (formula 8b) indicate that the maximumvertical pixel number (H) and the maximum horizontal pixel number (W)are obtained by dividing the maximum intra frame pixel number (Nfpx) bythe vertical pixel number calculation coefficient (Nαhpx) and thehorizontal pixel number calculation coefficient (Nαwpx), respectively.

[0246] The operation result signals Op3 a and Op3 b indicating themaximum vertical pixel number (H) and the maximum horizontal pixelnumber (W) which are obtained by the maximum vertical pixelnumber/maximum horizontal pixel number calculator 301 are inputted tothe 16-mulitple converter 302, and the 16-mulitple converter 302performs a rounding process for the maximum vertical pixel number (H)and the maximum horizontal pixel number (W), in the same manner as inthe 16-mulitple converter 202 according to the first embodiment. Then,the 16-mulitple converter 302 outputs rounding operation informationTrnd1 indicating a value (round1(H)) that is obtained by rounding themaximum vertical pixel number (H) to a multiple of 16, and roundingoperation information Trnd2 indicating a value (round2(H)) that isobtained by rounding the maximum horizontal pixel number (W) to amultiple of 16, to the second comparator 304.

[0247] Further, the second comparator 304 performs comparison betweenthe input image vertical pixel number (h) and the maximum vertical pixelnumber (H) (vertical pixel number comparison) and comparison between theinput image horizontal pixel number (w) and the maximum horizontal pixelnumber (W) (horizontal pixel number comparison), on the basis of thepixel number information Ihpx and Iwpx, and the rounding operationinformation Trnd1 and Trnd2, and outputs a comparison result signal Scm2a indicating the result of the vertical pixel number comparison, and acomparison result signal Scm2 b indicating the result of the horizontalpixel number comparison, to the AND unit 305.

[0248] Then, the AND unit 305 takes an AND of the comparison resultsignals Scm1, Scm2, and Scm2 b which are outputted from the comparators303 and 304, and outputs a signal CSjd indicating the final result ofthe judgement as to the coding capability/incapability.

[0249] As described above, the moving picture coding apparatus 10 b ofthe second embodiment includes the level analyzer 100 b that decides themaximum number of intra frame pixels (Nfpx) which can be coded and themaximum number of storage pixels (Nspx) which can be stored in a picturememory of a decoding apparatus in accordance with the level signal(signal of the level identifier) Lst that is inputted by the useroperation, and further decides the pixel detection coefficientinformation αpx indicating the vertical pixel number calculationcoefficient (Nαhpx) and the horizontal pixel number calculationcoefficient (Nαwpx) on the basis of the identification number signal Cidthat is inputted by the user operation, thereby judging whether codingof an input image is possible or not, and calculating the number ofreference candidate pictures which can be referred to at the interpicture prediction coding (reference picture maximum number) Nrpn, onthe basis of the maximum intra frame pixel number (Nfpx), the verticalpixel number calculation coefficient (Nαhpx), the horizontal pixelnumber calculation coefficient (Nαwpx), and the input image size (thenumber of vertical pixels (h) and the number of horizontal pixels (w)).Therefore, a decoding apparatus to which a bit stream from the movingpicture coding apparatus 10 b is to be supplied always can decode thebit stream satisfactorily, whereby picture prediction decoding dependingon the picture prediction coding on the coding end can be performed.Thereby, it is possible to design memory areas in the coding apparatusand the decoding apparatus corresponding to a coding method in whichthere is no restraint on the capacity of the memory area.

[0250] Further, in this second embodiment, the maximum number ofvertical pixels (H) and the maximum number of horizontal pixels (W) areobtained by dividing the maximum intra frame pixel number (Nfpx) by thevertical pixel number calculation coefficient (Nαhpx) and the horizontalpixel number calculation coefficient (Nαwpx), respectively. Therefore,the processes for obtaining the maximum vertical pixel number (H) andthe maximum horizontal pixel number (W) are facilitated as compared tothe first embodiment.

[0251] In this second embodiment, the level identifier corresponding tothe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the identification number corresponding to thevertical pixel number calculation coefficient (Nαhpx) and the horizontalpixel number calculation coefficient (Nαwpx) are parameters indicatingindependent coding conditions, respectively, while the identificationnumber may be correlated with the value of the level identifier.

[0252] In this case, when the coding level is decided, specific numericvalues of the vertical pixel number calculation coefficient (Nαhpx) andthe horizontal pixel number calculation coefficient (Nαwpx) as well asspecific numeric values of the maximum intra frame pixel number (Nfpx)and the maximum storage pixel number (Nspx) are decided on the basis ofthe value of the level identifier that indicates the decided level. Morespecifically, when the level signal Lst indicating the coding level thatis decided by the user is inputted to the level analyzer 100 b, thelevel analyzer 100 b outputs the information Ifps and Ispx indicatingthe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx) according to the level signal (level identifier)Lst, and further outputs pixel number calculation coefficientinformation αpx on the basis of the identification number signalcorresponding to the level identifier. Further, the bit stream Bsbcontains only the code H1 corresponding to the level signal Lst, andthus the code H2 corresponding to the identification number signal Cidis not transmitted to the decoding end.

[0253] In this second embodiment, the moving picture coding apparatustransmits the code H1 of the level signal Lst corresponding to themaximum intra frame pixel number (Nfpx) and the maximum storage pixelnumber (Nspx), which has been selected by the user, and the code H2 ofthe identification number signal Cid corresponding to the vertical pixelnumber calculation coefficient (Nαhpx) and the horizontal pixel numbercalculation coefficient (Nαwpx), which has been selected by the user, tothe decoding end. However, the moving picture coding apparatus mayencode the pixel number calculation coefficient information αpxindicating arbitrary vertical pixel number calculation coefficient(Nαhpx) and horizontal pixel number calculation coefficient (Nαwpx)which are decided by the user, and output the encoded pixel numbercalculation coefficient information αpx to the decoding end, in place ofthe code H2 of the identification number signal Cid.

[0254] In this case, the maximum intra frame pixel number (Nfpx) and themaximum storage pixel number (Nspx) are set at specific valuescorresponding to the level identifier that indicates the selected codinglevel on the basis of the Table T1, while specific values of thevertical pixel number calculation coefficient (Nαhpx) and the horizontalpixel number calculation coefficient (Nαwpx) are arbitrarily set by theuser. That is, when the level signal Lst indicating the decided codinglevel is inputted to the level analyzer 100 b under the control of theuser, the level analyzer 100 b outputs the information Ifpx indicatingthe maximum intra frame pixel number (Nfpx) that is decided on the basisof the table T1 in accordance with the level signal Lst, to the codingcapability judgment unit 108 b, and outputs the information Ispxindicating the maximum storage pixel number (Nspx) that is decided onthe basis of the table T1, to the maximum reference picture calculator109 a. The bit stream Bsb contains the code H1 corresponding to thelevel signal Lst and the code corresponding to the pixel numbercalculation coefficient information αpx, and accordingly the code H1corresponding to the level signal Lst and the code corresponding to thepixel number calculation coefficient information αpx are transmitted tothe decoding end.

[0255] Further, in this second embodiment, the table T2 in which pluralidentification numbers are correlated with pairs of the vertical pixelnumber calculation coefficient and the vertical pixel number calculationcoefficient (FIG. 17(a)) is employed as the table that defines thecorrespondence between plural identification numbers, and the verticalpixel number calculation coefficient and vertical pixel numbercalculation coefficient. However, in place of the table T2, a table T2 ain which the values of the identification number are correlated with thevertical pixel number calculation coefficients (FIG. 17(b) and a tableT2 b in which the values of the identification number are correlatedwith the horizontal pixel number calculation coefficients (FIG. 17(c))may be employed.

[0256] Further, in this second embodiment, the decision of theidentification number by the user is performed with referring to thetable T2 as shown in FIG. 17(a), while the decision of theidentification number by the user may be performed using a following(formula 9), in place of the table T2 shown in FIG. 17(a).

(Identification number)=transB (vertical pixel number calculationcoefficient, horizontal pixel number calculation coefficient)  (formula9)

[0257] Here, trans B( ) is a sign indicating an operation for obtainingthe value of the identification number, using the vertical pixel numbercalculation coefficient and the horizontal pixel number calculationcoefficient as arguments.

[0258] Further, in place of the table T2 a that defines thecorrespondence between the values of the identification number and thevertical pixel number calculation coefficients (FIG. 17(b)) and thetable T2 b that defines the correspondence between the values of theidentification number and the horizontal pixel number calculationcoefficients (FIG. 17(c)), following (formula 9a) and (formula 9b) maybe employed.

(Value of the identification number)=transBa (vertical pixel numbercalculation coefficient)  (formula 9a)

(Value of the identification number)=transBb (horizontal pixel numbercalculation coefficient)  (formula 9b)

[0259] Here, transBa ( ) is a sign that indicates an operation forobtaining a value of the identification number, using the vertical pixelnumber calculation coefficient as an argument. According to the (formula9a), when the user designates the vertical pixel number calculationcoefficient for the input image that can be coded by the moving picturecoding apparatus, the corresponding value of the identificationidentifier is decided.

[0260] Further, transBb ( ) is a sign that indicating an operation forobtaining a value of the identification number, using the horizontalpixel number calculation coefficient as an argument. According to the(formula 9b), when the user designates the horizontal pixel numbercalculation coefficient for the input image that can be coded by themoving picture coding apparatus, the corresponding value of theidentification number is decided.

[0261] In the above first embodiment, the maximum number of verticalpixels (H) and the maximum number of horizontal pixels (W) are obtainedby the (formula 1), (formula 2a), (formula 2b), (formula 3a), and(formula 3b), while in this second embodiment, the maximum number ofvertical pixels (H) and the maximum number of horizontal pixels (W) areobtained by the (formula 1), (formula 2a), (formula 2b), (formula 8a),and (formula 8b). However, the method for obtaining the maximum verticalpixel number (H) and the maximum horizontal pixel number (W) are notlimited to those described in the first and second embodiments.

[0262] [Embodiment 3]

[0263]FIG. 6 is a block diagram for explaining a moving picture codingapparatus 10 c according to a third embodiment of the present invention.

[0264] The moving picture coding apparatus 10 c of the third embodimenthas, in place of the level analyzer 100 a and the coding capabilityjudgment unit 108 a of the moving picture coding apparatus 10 aaccording to the first embodiment, a level analyzer 100 c that outputsinformation indicating the maximum image size (maximum image sizeinformation) Impx together with the maximum intra frame pixel numberinformation Ifpx and the maximum storage pixel number information Ispx,in accordance with the inputted level signal Lst and identificationnumber signal Sid, and a coding capability judgment unit 108 c thatjudges whether coding of the input image is possible or not on the basisof the maximum intra frame pixel number information Ifpx, the maximumimage size information Impx, and the input image size information Ipx.

[0265] Here, the identification number signal Sid indicates a value ofthe identification number decided by the user's operation, and theidentification number identifies a specific value of the maximum imagesize as an additional coding condition. The level analyzer 100 cincludes the information of the table T1 shown in FIG. 15, andinformation of a table T3 shown in FIG. 18(a). The table T1 definescorrespondence between the value of the identification number, and themaximum intra frame pixel number and the maximum storage pixel number.The table T3 shows correspondence between the value of theidentification number, and the maximum vertical pixel number (H) andhorizontal pixel maximum number (W). Further, the maximum image sizeinformation Impx is composed of information indicating the maximumnumber (H) of vertical pixels (vertical pixel maximum numberinformation) Imhpx, and information indicating the maximum number (W) ofhorizontal pixels (horizontal pixel maximum number information) Imwpx.The bit stream generator 103 of the moving picture coding apparatus 10 cvariable-length-codes the output data (coded data) Cd from theprediction residual encoder 102, and outputs a bit stream Bsc that isobtained by adding codes corresponding to the motion vector MV, the modesignal Ms, the level signal Lst, and the identification number signalSid, to a bit stream obtained by the variable length coding.

[0266] Constructions of the other components of the moving picturecoding apparatus 10 c according to the third embodiment are the same asthose of the moving picture coding apparatus 10 a of the firstembodiment.

[0267]FIG. 14(c) shows a data structure of the bit stream Bsccorresponding to an input image.

[0268] The bit stream Bsc is composed of a header area Hc that containsvarious kinds of header information, and a sequence data part Dsq thatcontains coded data (a bit stream) corresponding to image data of eachpicture.

[0269] In the header area Hc of the bit stream Bsc, a code H1corresponding to the level identifier and a code H3 corresponding to theidentification number signal Sid are included as header information.Further, in the sequence data part Dsq of the bit stream Bsc, a sequenceheader Sh indicating the size of the input image, i.e., the input imagevertical pixel number and the input image horizontal pixel number areincluded. More specifically, the code H3 is obtained by encoding theidentification number signal Sid that indicates a value of theidentification number for identifying the maximum vertical pixel numberand the maximum horizontal pixel number as shown in FIG. 18(a).

[0270]FIG. 7 is a diagram illustrating a specific construction of thecoding capability judgment unit 108 c.

[0271] The coding capability judgment unit 108 c is constituted only bythe multiplier 206, the first comparator 203, the second comparator 204,and the AND unit 205 of the coding capability judgment unit 108 aaccording to the first embodiment. In place of the outputs Trnd1 andTrnd2 from the 16-mulitple converter 202 in the coding capabilityjudgment unit 108 a according to the first embodiment, the maximumvertical pixel number information Imhpx indicating the maximum number ofvertical pixels (H) and the maximum horizontal pixel number informationImwpx indicating the maximum number of horizontal pixels (W) is inputtedfrom the level analyzer 10 c to the second comparator 204 as informationindicating the maximum image size (maximum image size information) Impx.

[0272] Next, the operation will be described.

[0273] The operation of the moving picture coding apparatus 10 caccording to the third embodiment is different from the operation of themoving picture coding apparatus 10 a of the first embodiment only in theoperations of the level analyzer 100 c, the coding capability judgmentunit 108 c, and the bit stream generator 103.

[0274] For the moving picture coding apparatus 10 c according to thethird embodiment, before the coding of an input image is performed, arequired level is selected from plural preset coding levels to be employas coding conditions, on the basis of the constructions of the memory orthe like in the moving picture coding apparatus 10 c, and a constructionof a memory or the like in the moving picture decoding apparatus towhich coded data are supplied, and further a predetermined level isselected from among plural levels of the identification number, whichare employed as additional coding conditions. To be more specific, theselection of the coding level is performed by the user with referring tothe table T1, and the level signal (level identifier) Lst indicating theselected level is inputted to the moving picture coding apparatus 10 cunder the control of the user. The selection of the level of theidentification number is performed by the user with referring to thetable T3, and the identification number signal Sid indicating theidentification number corresponding to the selected level is inputted tothe moving picture coding apparatus 10 c under the control of the user.

[0275] Here, the coding level, the maximum intra frame pixel number, andthe maximum storage pixel number are identical to those of the firstembodiment. In addition, the table T3 shown in FIG. 18(a) defines fourlevels of the identification number, and these levels of theidentification number correspond to values (1)˜(4) of the identificationnumber, respectively. The values (1)˜(4) of the identification numberare correlated with specific values of the maximum vertical pixel number(H) and the maximum horizontal pixel number (W), respectively.

[0276] In the moving picture coding apparatus 10 c, when the levelsignal Lst and the identification number signal Cid which are inputtedby the user' operation are supplied to the level analyzer 100 c, thelevel analyzer 100 c refers to the table T1 (FIG. 15) and the table T3(FIG. 18(a)) which are held therein, and outputs the maximum intra framepixel number information Ifpx and the maximum storage pixel numberinformation Ispx corresponding to the coding level indicated by thelevel signal Lst, which has been selected by the user, and furtheroutputs the maximum image size information Imps corresponding to thelevel of the identification number indicated by the identificationnumber signal Cid, which has been selected by the user. The maximumintra frame pixel number information Ifpx and the maximum image sizeinformation Impx is inputted to the coding capability judgment unit 108c, and the maximum storage pixel number information Ispx is inputted tothe maximum reference picture calculator 109 a.

[0277] Then, when image data Id of a moving picture (input image) isinputted to the picture memory 101 in units of pictures in the displayorder, image data corresponding to each picture are successively storedin the picture memory 101, and the stored image data SId are outputtedfrom the picture memory 101 in units of blocks (macroblocks) thatconstitute the picture in the coding order. At this time, informationindicating the size of the input data (input image size information) Ipxis outputted from the picture memory 101 to the coding capabilityjudgment unit 108 c and the maximum reference picture calculator 109 a.

[0278] Then, the coding capability judgment unit 108 c judges whethercoding of the input image is possible or not, on the basis of the inputimage size information Ipx outputted from the picture memory 101, andthe maximum intra frame pixel number information Ifpx and the maximumimage size information Impx outputted from the level analyzer 100 c, andoutputs a signal indicating the judgement result (judgement resultsignal) CSjd to the control unit 110.

[0279] When the judgement result signal CSjd indicates that the codingof the input image is possible, the control unit 110 performs switchingbetween a mode of performing inter picture prediction coding for imagedata and a mode of performing intra picture prediction coding for imagedata, on the basis of the image data SId from the picture memory 101,and outputs control signals for the respective components. Therespective components of the moving picture coding apparatus 10 c arecontrolled in accordance with control signals Sct1, Sct2, . . . , Sctnfrom the control unit 110 according to the judgement result signal CSjd,like in the first embodiment.

[0280] Further, the maximum reference picture calculator 109 acalculates the maximum number of reference pictures (Nrpn) on the basisof the maximum storage pixel number information Ispx, the input imagevertical pixel number information Ihpx, and the input image horizontalpixel number information Iwpx, and outputs information indicating thecalculated number (Nrpn) (reference picture maximum number information)Irpn.

[0281] In this third embodiment, when the inter picture predictioncoding mode is selected, the inter picture prediction coding for theinput image is performed in the same manner as the first embodiment,while when the intra picture prediction coding is selected, the intrapicture prediction coding for the input image is performed in the samemanner as the first embodiment.

[0282] In the third embodiment, however, when the inter pictureprediction coding mode is selected, the bit stream generator 103generates a bit stream corresponding to prediction residual coded dataCd that is outputted from the prediction residual encoder 102, andoutputs the generated bit stream together with a code corresponding tothe motion vector MV from the motion vector estimation unit 106, a codecorresponding to the mode signal Ms from the control unit 110, a codecorresponding to the level signal Lst, and a code corresponding to theidentification number signal Sid, as a bit stream Bsc (see FIG. 14(c)).When the intra picture prediction coding mode is selected, the bitstream generator 103 generates a bit stream corresponding to the codeddata Cd that is outputted from the encoder 102, and outputs thegenerated bit stream together with a code corresponding to the modesignal Ms from the control unit 110, a code corresponding to the levelsignal Lst, and a code corresponding to the identification number signalSid, as a bit stream Bsc (see FIG. 14(c)).

[0283] Next, a specific operation of the coding capability judgment unit108 c in the moving picture coding apparatus 10 c will be described withreference to FIG. 7.

[0284] The coding capability judgment unit 108 c of the moving picturecoding apparatus 10 c according to the third embodiment judges whethercoding of an input image is possible or not, on the basis of theabove-mentioned conditional formulas (formula 1), (formula 2a), and(formula 2b). In other words, the maximum number of vertical pixels (H)and the maximum number of horizontal pixels (W) are obtained on thebasis of the (formula 1), (formula 2a), (formula 2b), and theinformation of the table T3 shown in FIG. 18(a). Here, the (formula 1),(formula 2a), and (formula 2b) are defined by claim 3.

[0285] More specifically, in this third embodiment, the level analyzer100 c includes the table T3 as shown in FIG. 18(a) and, in the codingcapability judgment unit 108 c of the third embodiment, the informationImhpx and Imwpx indicating the maximum vertical pixel number (H) and themaximum horizontal pixel number (W), which is outputted from the levelanalyzer 100 c on the basis of the table T3, is directly input to thesecond comparator 204.

[0286] Then, the second comparator 204 performs comparison between theinput image vertical pixel number (h) and the maximum vertical pixelnumber (H) (i.e., vertical pixel number comparison), and comparisonbetween the input image horizontal pixel number (w) and the maximumhorizontal pixel number (W) (i.e., horizontal pixel number comparison),and outputs a comparison result signal Scm2 a indicating the result ofthe vertical pixel number comparison, and a comparison result signalScm2 b indicating the result of the horizontal pixel number comparisonto the AND unit 205.

[0287] As described above, the moving picture coding apparatus 10 c ofthe third embodiment includes the level analyzer 100 c that decides themaximum number of intra frame pixels (Nfpx) which can be coded and themaximum number of storage pixels (Nspx) which can be stored in a picturememory of a decoding apparatus, in accordance with the level signal(level identifier signal) Lst that is inputted under the control of theuser, and decides the maximum number of vertical pixels (H) and themaximum number of horizontal pixels (W) in accordance with theidentification number signal Sid that is inputted under the control ofthe user, thereby judging whether coding of the input image is possibleor not on the basis of the maximum intra frame pixel number (Nfpx), themaximum vertical pixel number (H), the maximum horizontal pixel number(W), and the input image size (the number of vertical pixels (h) and thenumber of horizontal pixels (w)), and calculating the number ofreference candidate pictures (reference picture maximum number) Nrpnwhich can be referred to at the inter picture prediction coding.Therefore, the decoding apparatus to which a bit stream from the movingpicture coding apparatus 10 c is supplied can always decode the bitstream satisfactorily, whereby picture prediction decoding correspondingto the picture prediction coding on the coding end can be performed.Accordingly, memory areas in the coding apparatus and the decodingapparatus corresponding to a coding method in which there is norestraint on the capacity of the memory area can be designed.

[0288] In this third embodiment, the values indicated by the informationImpx that is supplied from the level analyzer 100 c are employed as themaximum vertical pixel number (H) and the maximum horizontal pixelnumber (W). Therefore, the process for obtaining the maximum verticalpixel number (H) and the maximum horizontal pixel number (W) isfacilitated as compared to the first embodiment.

[0289] In this third embodiment, the level identifier corresponding tothe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the identification number corresponding to themaximum vertical pixel number (H) and the maximum horizontal pixelnumber (W) are used as parameters that indicate independent codingconditions, respectively. However, the values of the identificationnumber may be correlated with the values of the level identifier.

[0290] In this case, specific values of the maximum intra frame pixelnumber (Nfpx) and the maximum storage pixel number (Nspx) are valueswhich are decided on the basis of the table T1 according to the levelidentifier that indicates the selected coding level, and furtherspecific values of the maximum vertical pixel number (H) and the maximumhorizontal pixel number (W) are values which are decided on the basis ofthe table T3 according to the identification number that is correlatedwith the selected coding level. That is, when the level signal Lstindicating the decided coding level is inputted to the level analyzer100 c under the control of the user, the level analyzer 100 c outputsthe information Ifpx and Ispx indicating the maximum intra frame pixelnumber (Nfpx) and the maximum storage pixel number (Nspx) in accordancewith the level signal Lst, and further outputs the maximum image sizeinformation Impx on the basis of the identification number correspondingto the level identifier. In addition, the bit stream Bsc includes onlythe code H1 corresponding to the level signal Lst, and thus the code H3corresponding to the identification number signal Sid is not transmittedto the decoding end.

[0291] In this third embodiment, the moving picture coding apparatustransmits the code of the level signal Lst corresponding to the maximumintra frame pixel number (Nfpx) and the maximum storage pixel number(Nspx) which have been selected by the user, and the code H3 of theidentification number signal Sid corresponding to the maximum verticalpixel number (H) and the maximum horizontal pixel number (W) which havebeen selected by the user, to the decoding end. However, the movingpicture coding apparatus may encode the maximum image size informationImpx indicating the maximum vertical pixel number (H) and the maximumhorizontal pixel number (W) which have been arbitrarily decided by theuser, to transmit the coded maximum pixel number information to thedecoding end, in place of the code H3 of the identification numbersignal Sid.

[0292] In this case, specific values of the maximum intra frame pixelnumber (Nfpx) and the maximum storage pixel number (Nspx) are valueswhich are decided on the basis of the table T1 according to the levelidentifier that indicates the selected coding level, while specificvalues of the maximum vertical pixel number (H) and the maximumhorizontal pixel number (W) are arbitrarily decided by the user. Thatis, when the level signal Lst indicating the decided coding level isinput to the level analyzer 100 c under the control of the user, thelevel analyzer 100 c outputs the information Ifpx indicating the maximumintra frame pixel number (Nfpx) that is selected from the table T1 inaccordance with the level signal Lst, to the coding capability judgmentunit 108 c, and outputs the information Ispx indicating the maximumstorage pixel number (Nspx) that is selected from the table T1, to themaximum reference picture calculator 109 a. Further, the maximum imagesize information Impx indicating specific values of the maximum verticalpixel number (H) and the maximum horizontal pixel number (W) which havebeen decided by the user is inputted directly from outside to the codingcapability judgment unit 108 c. In addition, the bit stream Bsc includesthe code H1 corresponding to the level signal Lst and the codecorresponding to the maximum image size information Impx, and thus thecode H1 corresponding to the level signal Lst and the code correspondingto the maximum image size information Impx are transmitted to thedecoding end.

[0293] Further, in this third embodiment, the table T3 in which pluralvalues of the identification number are correlated with pairs of themaximum vertical pixel number and the maximum horizontal pixel number(FIG. 18(a)) is employed as a table that defines correspondence betweenplural values of the identification number, and the vertical pixelnumber calculation coefficient and vertical pixel number calculationcoefficient. However, a table T3 a in which values of the identificationnumber are correlated with the maximum vertical pixel numbers (H) (FIG.18(b)), and a table T3 b in which values of the identification numberare correlated with the maximum horizontal pixel numbers (W) (FIG.18(c)) may be employed in place of the table T3. Further, it goeswithout saying that the number of combinations of the maximum verticalpixel number and the maximum horizontal pixel number in the tables T3,T3 a, and T3 b, and their values are not limited to those shown in FIGS.18(a) to 18(c).

[0294] Further, in the descriptions of the first and second embodiments,limitations on the number of vertical pixels and the number ofhorizontal pixels in an input image that can be coded are imposed by the(formula 2a) and (formula 2b), while the limitation the size of theinput image that can be coded may be imposed by limiting only one of thenumber of vertical pixels and the number of horizontal pixels.

[0295] Further, it is also possible to judge whether the coding of aninput image is possible or not, only on the basis of comparison betweenthe maximum intra frame pixel number, and the numbers of vertical andhorizontal pixels in the input image as indicated by the (formula 1),without utilizing the (formula 2a), (formula 2b), (formula 3a), (formula3b), (formula 8a), and (formula 8b) which have been employed in any ofthe above-mentioned embodiments.

[0296] In the third embodiment, the decision of the value of theidentification number is performed by the user with referring to thetable T3 shown in FIG. 18(a), but the decision of the identificationnumber may be performed by the user using a following (formula 10), inplace of the table T3 shown in FIG. 18(a).

(Identification number)=transC (the maximum number of vertical pixels,the maximum number of horizontal pixels)  (formula 10)

[0297] Here, transC is a sign that indicates an operation for obtainingan identification number, using the maximum number of vertical pixelsand the maximum number of horizontal pixels as arguments. According tothe (formula 10), when the maximum number of vertical pixels and themaximum number of horizontal pixels in the input image which can becoded by the moving picture coding apparatus are designated by the user,the corresponding value of the identification number is decided.

[0298] Further, following (formula 10a) and (formula 10b) may beemployed in place of the table T3 a indicating the correspondencebetween values of the identification number and the maximum verticalpixel numbers (FIG. 18(b)) and the table T3 b indicating thecorrespondence between values of the identification number and themaximum horizontal pixel numbers (FIG. 18(c)).

(Identification number)=transCa (the maximum number of verticalpixels)  (formula 10a)

(Identification number)=transCb (the maximum number of horizontalpixels)  (formula 10b)

[0299] Here, transCa( ) is a sign indicating an operation for obtaininga value of the identification number, using the maximum number ofvertical pixels as an argument. According to the (formula 10a), when theuser designates the maximum number of vertical pixels in the input imagewhich can be coded by the moving picture coding apparatus, thecorresponding value of the identification number is decided.

[0300] Further, transCb( ) is a sign indicating an operation forobtaining a value of the identification number, using the maximum numberof horizontal pixels as an argument. According to the (formula 10b),when the user designates the maximum number of horizontal pixels in theinput image which can be coded by the moving picture coding apparatus,the corresponding value of the identification number is decided.

[0301] [Embodiment 4]

[0302]FIG. 8 is a block diagram for explaining a moving picture codingapparatus 10 d according to a fourth embodiment of the presentinvention.

[0303] The moving picture coding apparatus 10 d of the fourth embodimenthas, in place of the maximum reference picture calculator 109 a of themoving picture coding apparatus 10 a according to the first embodiment,a maximum reference picture calculator 109 d that calculates the maximumnumber of reference pictures (Nrpn) on the basis of the size informationIpx for an input image (input image vertical pixel number informationIhpx and input image horizontal pixel number information Iwpx), themaximum storage pixel number information Ispx, and display waiting pixelnumber information Idwp, and outputs information indicating thecalculated value (Nrpn) (i.e., reference picture maximum numberinformation) Irpn.

[0304] Here, the display waiting pixel number information Idwp isinformation that indicates the number of display wait pictures. Thedisplay wait pictures are previously decoded pictures that are notemployed as reference pictures, as described above with reference toFIG. 26, and image data of the pictures are stored in a picture memoryof a decoding apparatus until they are displayed. Further, the controlof the picture memory according to the fourth embodiment is performedadaptively to the control of a picture memory in a decoding apparatus,so that image data of a picture that is not employed as a referencepicture is deleted from the picture memory immediately after display ofthe picture is finished.

[0305] Constructions of other components in the moving picture codingapparatus 10 d according to the fourth embodiment are the same as thosein the moving picture coding apparatus 10 a of the first embodiment.

[0306]FIG. 9 is a diagram illustrating a specific construction of themaximum reference picture calculator 109 d.

[0307] This maximum reference picture calculator 109 d includes, inaddition to the multiplier 401, the divider 402, the subtractor 403, andthe constant storage unit 404 in the maximum reference picturecalculator 109 a according to the first embodiment, a subtractor 405that subtracts the number of display wait pictures (Ndwp) in the picturememory from the number of pictures indicated by the operation output Sd1from the subtractor 403, on the basis of the picture number informationIdwp from the picture memory 105, and outputs an output signal Sd2 fromthe subtractor 405 as reference picture maximum number information Irpn.

[0308] Next, its operation will be described.

[0309] The operation of the moving picture coding apparatus 10 daccording to the fourth embodiment is different from that of the movingpicture coding apparatus 10 a according to the first embodiment only inthe operation of the maximum reference picture calculator 109 d.

[0310] Thus, only the operation of the maximum reference picturecalculator 109 d will be described hereinafter with reference to FIG. 9.

[0311] The maximum reference picture calculator 109 d of the movingpicture coding apparatus 10 d according to the fourth embodimentcalculates the maximum number of reference candidate pictures which areemployed at the inter picture prediction coding, according to anoperation indicated by a following (formula 11). Here, the (formula 11)is defined by claim 6.

Nrpn=Nspx÷(h×w)−1−Ndwp  (formula 11)

[0312] Here, h designates the number of vertical pixels in the inputimage (target picture to be coded), and w designates the number ofhorizontal pixels in the input image (the target picture). Nrpndesignates the maximum number of reference pictures, Nspx designates themaximum number of storage pixels, and Ndwp designates the number ofdisplay waiting decoded pictures. In this fourth embodiment, the maximumstorage pixel number Nspx is the maximum value of the total number ofpixels corresponding to all storage pictures whose image data are storedin a picture memory of a moving picture decoding apparatus that decodesa bit stream obtained by the moving picture coding apparatus 10 a. Thestorage pictures are reference pictures, a target picture to be decoded,and display waiting decoded pictures.

[0313] The maximum reference picture calculator 109 d calculates thetotal number of pixels in one frame (h×w), corresponding to the size ofthe input image on the basis of input image vertical pixel numberinformation Ihpx and input image horizontal pixel number informationIwpx. More specifically, the multiplier 401 multiplies the number ofvertical pixels (h) in the input image, which is indicated by the inputimage vertical pixel number information Ihpx, by the number ofhorizontal pixels (w), which is indicated by the input image horizontalpixel number information Iwpx, and outputs an operation output Shwindicating the multiplication result (h×w).

[0314] The divider 402 divides the maximum storage pixel number (Nspx)by the multiplication result (h×w) on the basis of the operation outputShw from the multiplier 401 and the maximum storage pixel numberinformation Ispx from the level analyzer 100 d, and outputs an operationoutput signal Dpm indicating the division result (Nspx/(h×w)).

[0315] The subtractor 403 subtracts 1 from the division result(Nspx/(h×w)) on the basis of the output signal Dpm from the divider 402and the numeric value information Sn1 from the constant storage unit404, and outputs a subtraction output signal Sd1 indicating thesubtraction result (Nspx/(h×w)−1).

[0316] Further, the subtractor 405 subtracts the number of display waitpictures (Ndwp) from the subtraction result (Nspx/(h×w)−1) on the basisof the subtraction output signal Sd1, and the picture number informationIdwp from the picture memory, thereby deciding the maximum number ofreference pictures.

[0317] The reason why the subtractors 403 and 405 subtracts 1 and thenumber of display wait pictures (Ndwp) from the division result(Nspx/(h×w)), respectively, is that decoded image data of a targetpicture to be decoded and display wait pictures, as well as image dataof reference candidate pictures which are employed at the inter pictureprediction decoding must be stored in the picture memory of the decodingapparatus.

[0318] As described above, the moving picture coding apparatus 10 d ofthe fourth embodiment includes the level analyzer 100 a that decides themaximum number of intra frame pixels (Nfpx) which can be coded and themaximum number of storage pixels (Nspx) which can be stored in thepicture memory of the decoding apparatus, on the basis of the levelsignal LSt that indicates a coding level designated by the user, therebyperforming the judgement as to whether the coding of an input image ispossible or not on the basis of the maximum intra frame pixel number(Nfpx) and the input image size (the number of vertical pixels Nhpx andthe number of horizontal pixels Nwpx), and calculating the number ofreference candidate pictures which can be referred to at the interpicture prediction coding (reference picture maximum number) Nrpn.Therefore, a decoding apparatus to which a bit stream from the movingpicture coding apparatus 10 b is supplied can always decode the bitstream satisfactorily, whereby picture prediction decoding correspondingto picture prediction coding on the coding end can be performed.Accordingly, memory areas of the coding apparatus and the decodingapparatus that are compliant with a coding method in which there is norestraint on the capacity of the memory areas can be designed.

[0319] In this fourth embodiment, the maximum number of referencepictures which are stored in the picture memory is decided in view ofthe number of display wait pictures (Ndwp), whereby the picture memoryin which image data of reference candidate pictures are stored can beefficiently employed according to the status of the processing for imagedata.

[0320] In the fourth embodiment, the maximum storage pixel number Nspxis the maximum value of the total number of pixels corresponding to allstorage pictures whose image data are stored in a picture memory of amoving picture decoding apparatus that decodes a bit stream obtained bythe moving picture coding apparatus 10 a, and the storage pictures arereference pictures, a target picture to be decoded, and display waitingdecoded pictures. However, it is possible to define the maximum storagepixel number not to include the number of pixels corresponding to thetarget picture to be decoded.

[0321] In this case, a following (formula 11a) is employed in place ofthe (formula 11).

Nrpn=Nspx÷(h×w)−Ndwp  (formula 11a)

[0322] Thus, the maximum reference picture calculator 109 d shown inFIG. 9 decides the maximum number of reference pictures, withoutperforming the operation of subtracting 1 from the division result(Nspx/(h×w)).

[0323] Here, h designates the number of vertical pixels in a targetpicture to be coded, w designates the number of horizontal pixels in thetarget picture, Nrpn designates the maximum number of referencepictures, Nspx designates the maximum number of storage pixels, and Ndwpdesignates the number of display wait pictures.

[0324] In this fourth embodiment, the control of the picture memory isperformed adaptively to the control of a picture memory in the decodingapparatus for deleting image data of pictures which are not employed asreference pictures from the picture memory immediately after the displayof the pictures is finished. However, the image data of pictures whichare not employed as reference pictures may be deleted at a time otherthan immediately after the display as described in the fourthembodiment.

[0325] For example, the control of the picture memory according to thefourth embodiment may be performed adaptively to the control of thepicture memory in the decoding apparatus for deleting image data of apicture which is stored in the picture memory but is not used as areference picture, from the picture memory after the display time of onepicture expires after the picture has been displayed.

[0326] [Embodiment 5]

[0327]FIG. 10 is a block diagram for explaining a moving picturedecoding apparatus 50 a according to a fifth embodiment of the presentinvention.

[0328] The moving picture decoding apparatus 50 a according to the fifthembodiment receives a bit stream corresponding to plural pictures thatconstitute a moving picture, and decodes the bit stream in predetermineddata processing units, i.e., in units of blocks. More specifically, thismoving picture decoding apparatus 50 a decodes a bit stream Bsa (seeFIG. 14(a)) generated by the moving picture coding apparatus 10 aaccording to the first embodiment. Here, the block is a macroblock thatis composed of 16 vertical pixels×16 horizontal pixels.

[0329] That is, this moving picture decoding apparatus 50 a includes abit stream analyzer 501 that analyzes an inputted bit stream Bsa, andoutputs various kinds of header information that is stored in a headerarea Ha of the bit stream Bsa, and data stored in a sequence data partDsq of the bit stream Bsa. Here, a level identifier H1 is included inthe header area Ha as one kind of header information. In addition, thesequence data part Dsq contains a sequence header Sh, and furthercontains information Ms of a coding mode, coded data Cd, information MVof a motion vector, and the like, corresponding to each macroblock.Further, information indicating the size of an input image that has beena target of the coding process on the coding end (input image sizeinformation) Ipx is included in the sequence header Sh. This input imagesize information Ipx is composed of information Ihpx indicating thenumber of vertical pixels (Nhpx) of the input image, and informationIwpx indicating the number of horizontal pixels (Nwpx) of the inputimage.

[0330] The moving picture decoding apparatus 50 a includes a predictionresidual decoder 502 that decompressively decodes coded data Cd from thebit stream analyzer 501, and outputs decoded residual data Dd of thetarget block; an adder 511 that adds the decoded residual data Dd of thetarget block and predictive data Pd for the target block, and outputsimage data of the target block (hereinafter, referred to as decodeddata) Rd; and a picture memory 503 that temporarily stores one of theoutput data Dd from the prediction residual decoder 502 and the outputdata Rd from the adder 511, and outputs the stored decoded data Ed asdata DRd of a picture that is to be referred to at the decoding of thetarget block in accordance with a picture designation signal DSpd. Here,in the picture memory 503, image data of decoded pictures which arearranged in the order of decoding are reordered in the order of display.The image data of the decoded pictures which have been reordered in theorder of display are outputted from the picture memory 503 in units ofpictures, as image data Od of the output image.

[0331] The moving picture decoding apparatus 50 a includes a motioncompensation decoder 504 that generates predictive data Pd for thetarget block on the basis of a motion vector MV from the bit streamanalyzer 501 and the output data (reference candidate picture data) DRdfrom the picture memory 503; and a motion vector storage unit 505 thatstores the motion vector MV of a block, which has been supplied to themotion compensation decoder 504.

[0332] The moving picture decoding apparatus 50 a includes a selectorswitch 508 that selects one of the output data Dd from the predictionresidual decoder 502 and the output data Rd from the adder 511, andoutputs the selected data as selection data Ed. Here, the selectorswitch 508 has two input terminals Tc1 and Tc2, and one output terminalTd. In accordance with a switch control signal, the output terminal Tdis connected to one of the two input terminals Tc1 and Tc2.

[0333] The moving picture decoding apparatus 50 a of the fifthembodiment includes a level analyzer 509 a that outputs informationindicating the maximum number of intra frame pixels which can be decoded(Nfpx) (i.e., the maximum intra frame pixel number information) Ifpx,and information indicating the number of pixels corresponding to themaximum image data which can be stored in the picture memory of thedecoding apparatus (the maximum storage pixel number (Nspx)) (i.e., themaximum storage pixel number information) Ispx, in accordance with alevel signal (level identifier) Lst indicating a coding level from thebit stream analyzer 501. This level analyzer unit 509 includesinformation of the table T1 shown in FIG. 15. The table T1 definescorrespondence between the level identifier value, and the maximum intraframe pixel number and storage pixel maximum number.

[0334] The moving picture decoding apparatus 50 a includes a judgementunit (decoding capability judgment unit) 506 a that judges whetherdecoding of the inputted bit stream is possible or not, on the basis ofthe maximum intra frame pixel number information Ifpx that is outputtedfrom the level analyzer 509 a and information indicating the number ofvertical pixels (h) and the number of horizontal pixels (w) of the inputimage (input image size information) Ipx, which is outputted from thebit stream analyzer 501, and outputs a signal indicating the judgementresult (judgement result signal) DSjd. The moving picture decodingapparatus 50 a further includes a calculator (maximum reference picturecalculator) 507 a that calculates the number of reference candidatepictures (reference picture maximum number) Nrpn which can be referredto at inter picture prediction decoding, on the basis of the maximumstorage pixel number information Ispx and the input image sizeinformation Ipx, and outputs information Irpn indicating the calculatednumber Nrpn (reference picture maximum number).

[0335] The moving picture decoding apparatus 50 a further includes acontrol unit 510 that controls operations of the respective componentsof the moving picture decoding apparatus 50 a with control signals Dct1,Dct2, . . . , Dctn, on the basis of the judgement result signal DSjd andthe coding mode information Ms from the bit stream analyzer 501. Thiscontrol unit 510 controls the switch 508 with a predetermined controlsignal, according to the coding mode indicated by the mode signal Msfrom the bit stream analyzer 501. The control unit 510 further controlsoperations of the prediction residual decoder 502, the motioncompensation decoder 504, and the like with the control signals Dct1,Dct2, . . . , Dctn, on the basis of the judgement result signal DSjd.That is, when the judgement result signal DSjd indicates that decodingof the inputted bit stream Bsa is possible, the control unit 510controls the prediction residual decoder 502, the motion compensationdecoder 504, and the like, for executing the decoding of the inputtedbit stream Bsa. On the other hand, when the judgement result signal DSjdindicates that decoding of the inputted bit stream Bsa is impossible,the control unit 510 controls the prediction residual decoder 502, themotion compensation decoder 504, and the like, for not executing thedecoding of the inputted bit stream Bsa.

[0336] A specific construction of the decoding capability judgment unit506 a in the moving picture decoding apparatus 50 a according to thefifth embodiment is the same as that of the coding capability judgmentunit 108 a in the moving picture coding apparatus 10 a according to thefirst embodiment as shown in FIG. 2.

[0337] A specific construction of the maximum reference picturecalculator 507 a in the moving picture decoding apparatus 50 a accordingto the fifth embodiment is the same as that of the maximum referencepicture calculator 109 a in the moving picture coding apparatus 10 aaccording to the first embodiment as shown in FIG. 3.

[0338] Next, its operation will be described.

[0339] When the bit stream Bsa is inputted to the moving picturedecoding apparatus 50 a, initially the bit stream analyzer 501 analyzesthe bit stream Bsa to extract various kinds of information such as thecoding mode information Ms, motion vector information MV, and coded dataCd, from the bit stream Bsa. At that time, the bit stream analyzer 501simultaneously extracts various kinds of header information included inthe header area Ha of the bit stream Bsa, and outputs the headerinformation to the level analyzer 509 a, the decoding capabilityjudgment unit 506, and the maximum reference picture calculator 507 a.

[0340] The level analyzer 509 a decides the maximum number of intraframe pixels (Nfpx) and the maximum number of storage pixels (Nspx) withreferring to the table T1 (FIG. 15) that is retained therein, inaccordance with the level signal Lst corresponding to one kind of headerinformation H1 included in the header area Ha, and outputs maximum intraframe pixel number information Ifpx and storage pixel maximum numberinformation Ispx. The maximum intra frame pixel number information Ifpxis inputted to the decoding capability judgment unit 506 a, and themaximum storage pixel number information Ispx is inputted to the maximumreference picture calculator 507 a.

[0341] Then, the coding capability judgment unit 506 a judges whetherdecoding for the inputted bit stream Bsa is possible or not, on thebasis of the maximum intra frame pixel number information Ifpx from thelevel analyzer 509 a, and the input image size information Ipx (inputimage vertical pixel number information Ihpx and horizontal pixel numberinformation Iwpx) that has been extracted from the sequence header Sh ofthe bit stream Bsa by the bit stream analyzer 501, and outputs a signalindicating the result of judgement (judgement result signal) DSjd to thecontrol unit 510.

[0342] When the judgement result signal DSjd indicates that the codingof the inputted bit stream Bsa is possible, the control unit 510controls the moving picture decoding apparatus 50 a in accordance withthe control signals Dct1, Dct2, . . . , Dctn, for executing the decodingof the inputted bit stream Bsa, while when the judgement result signalDSjd indicates that the decoding of the inputted bit stream Bsa isimpossible, the control unit controls the respective components of themoving picture decoding apparatus 50 a in accordance with the controlsignals Dct1, Dct2, . . . , Dctn, for not executing the decoding of theinputted bit stream Bsa.

[0343] When the judgement result signal DSjd indicates that the decodingof the inputted bit stream Bsa is possible, the control unit 510performs switching between a mode of performing inter picture predictiondecoding for the bit stream Bsa and a mode of performing intra pictureprediction decoding for the bit stream Bsa according to the coding modeindicated by the mode signal Ms from the bit stream analyzer 501.

[0344] Then, when the mode of performing the inter picture predictioncoding is selected by the control unit 510, the switch 508 is controlledby a predetermined control signal from the control unit 510, so that theoutput terminal Td is connected to the second input terminal Tc2. On theother hand, when the mode of performing the intra picture predictioncoding is selected by the control unit 510, the switch 508 is controlledby a predetermined control signal from the control unit 510, so that theoutput terminal Td is connected to the first input terminal Tc1.

[0345] Further, the maximum reference picture calculator 507 acalculates the number of reference candidate pictures which can bereferred to at the inter picture prediction decoding (reference picturemaximum number) Nrpn on the basis of the maximum storage pixel numberinformation Ispx, and the vertical pixel number information Ihpx andhorizontal pixel number information Iwpx of the input image, and outputsinformation indicating the calculated number Nrpn (reference picturemaximum number information) Irpn to the motion compensation decoder 504.

[0346] Hereinafter, the operation in the case where the inter pictureprediction decoding mode is selected will be initially described.

[0347] When the motion vector information MV that has been extractedfrom the bit stream Bsa by the bit stream analyzer 501 is inputted tothe motion compensation decoder 504, the motion compensation decoder 504performs motion compensation for the target macroblock on the basis ofthe reference picture maximum number information Irpn from the maximumreference picture calculator 507 a, and the motion vectors MV of decodedmacroblocks and the motion vector MV of the target macroblock which arestored in the motion vector storage unit 505, with referring to apredetermined reference picture, and outputs predictive data Pdcorresponding to the target block, to the adder 511. At this time,decoded image data Ed corresponding to the decoded pictures are storedin the picture memory 503, as image data of reference candidatepictures, and a required picture among the reference candidate picturesis specified in the picture memory 503 as the reference picture inaccordance with a picture designation signal DSpd from the motioncompensation decoder 504.

[0348] Coded data Cd that has been extracted from the bit stream Bsa bythe bit stream analyzer 501 is decoded by the prediction residualdecoder 502, and prediction residual image data Dd that has beenobtained by the decoding is outputted to the adder 511.

[0349] The adder 511 performs addition between the prediction residualimage data Dd from the prediction residual decoder 502 and thepredictive data Pd from the motion compensation decoder 504, and outputsimage data Rd that is obtained by the addition to the picture memory 503via the switch 508. Then, the image data Rd of the target picture to bedecoded is written to the picture memory 503 as decoded data in units ofmacroblocks.

[0350] Then, image data of decoded pictures which are arranged in theorder of decoding are reordered in the order of display, and outputtedfrom the picture memory 503 as image data Od of an output image in unitsof pictures.

[0351] Next, the operation in the case where the intra pictureprediction coding mode is selected will be briefly described.

[0352] In this case, the coded data Cd extracted from the bit stream Bsaby the bit stream analyzer 501 are decoded by the prediction residualdecoder 502, and prediction residual image data Dd obtained by thedecoding is stored in the picture memory 503 as it is as decoded data Rdvia the switch 508.

[0353] Next, specific operations of the decoding capability judgmentunit 506 a and the maximum reference picture calculator 507 a in themoving picture decoding apparatus 50 a will be briefly described.

[0354] The decoding capability judgment unit 506 a of the moving picturedecoding apparatus 50 a according to the fifth embodiment judges whetherthe decoding of the inputted bit stream is possible or not, according tothe above-mentioned conditional formulae (formula 1), (formula 2a),(formula 2b), (formula 3a), and (formula 3b), like the coding capabilityjudgment unit 108 a of the moving picture coding apparatus 10 aaccording to the first embodiment.

[0355] More specifically, the decoding capability judgment unit 506 aperforms the operation indicated by (formula 1) on the basis of theinput image vertical pixel number information Ihpx and horizontal pixelnumber information Iwpx included in the input image size information Ipxthat has been outputted from the bit stream analyzer 501. In otherwords, the multiplication for obtaining the product (h×w) of the numberof vertical pixels (h) and the number of horizontal pixels (w) in theinput image is performed, and then comparison between the multiplicationresult (h×w) and the maximum intra frame pixel number (Nfpx) (i.e.,intra frame pixel number comparison) is performed. Next, the decodingcapability judgment unit 506 a calculates the maximum number of verticalpixels (H) and the maximum number of horizontal pixels (W) as indicatedby the (formula 3a) and (formula 3b), respectively, on the basis of theinput image vertical pixel number information Ihpx and horizontal pixelnumber information Iwps.

[0356] Here, the (formula 3a) and (formula 3b) indicate that the maximumvertical pixel number (H) and the maximum horizontal pixel number (W)are respectively the positive square root of a value that is obtained bymultiplying the product of the vertical pixel number (h) and thehorizontal pixel number (w) of the input image, by N. For example whenN=8, the (formula 3a) suggests that the maximum number of verticalpixels are decided so that the ratio between the number of verticalpixels and the number of horizontal pixels is smaller than 8:1, and the(formula 3b) suggests that the maximum number of horizontal pixels aredecided so that the ratio between the number of vertical pixels and thenumber of horizontal pixels is smaller than 1:8.

[0357] The decoding capability judgment unit 506 a further performs anoperation such as omission, raising, or half-adjust, for the maximumnumber of vertical pixels (H) and the maximum number of horizontalpixels (W) to be rounded to a multiple of 16, respectively, and thenperforms comparison between the input image vertical pixel number (h)and the rounded maximum number of vertical pixels (H) (vertical pixelnumber comparison), and comparison between the input image horizontalpixel number (w) and the rounded maximum number of horizontal pixels (W)(horizontal pixel number comparison).

[0358] Then, on the basis of the results of the intra frame pixel numbercomparison, the vertical pixel number comparison, and the horizontalpixel number comparison, the final judgement as to thecapability/incapability of decoding is performed.

[0359] The maximum reference picture calculator 507 a of the movingpicture coding apparatus 50 a according to the fifth embodimentcalculates the maximum number of reference candidate pictures which areemployed at the inter picture prediction decoding, according to theoperation indicated by the (formula 4).

[0360] The maximum reference picture calculator 507 a calculates thetotal number of pixels in one frame (h×w) as the size of the inputimage, on the basis of the vertical pixel number information Ihpx andthe horizontal pixel number information Iwpx for the input image fromthe coding analyzer 501.

[0361] Further, the maximum reference picture calculator 507 a performsan operation of dividing the maximum storage pixel number (Nspx) by themultiplication result (h×w), and further performs an operation ofsubtracting 1 from the division result (Nspx/(h×w)), thereby obtainingthe subtraction result (Nspx/(h×w)−1) as the maximum number of referencepictures.

[0362] As described above, the moving picture decoding apparatus 50 a ofthe fifth embodiment includes the level analyzer 509 a that decides themaximum number of intra frame pixels (Nfpx) which can be decoded and themaximum number of storage pixels (Nspx) which can be stored in thepicture memory 503 in accordance with the level signal Lst indicatingthe level identifier, which has been extracted from the bit stream Bsaby the bit stream analyzer 501, thereby judging whether decoding of theinputted bit stream Bsa is possible or not on the basis of the maximumintra frame pixel number (Nfpx) and the input image size (vertical pixelnumber Nfpx and horizontal pixel number Nwpx), and calculating thenumber of reference candidate pictures which can be referred to at theinter picture prediction decoding (reference picture maximum number)Nrpn. Therefore, a bit stream which can be decoded by the moving picturedecoding apparatus among bit streams which have been supplied from thecoding end can be determined by the level identifier, therebysatisfactorily performing picture prediction decoding corresponding tothe picture prediction coding on the coding end. Thereby, it is possibleto design a memory area in the decoding apparatus corresponding to thecoding method in which there is no restraint on the capacity of thememory area.

[0363] In this fifth embodiment, the table T1 in which pairs of themaximum intra frame pixel number and the maximum storage pixel numberare correlated with the coding levels (values of the level identifier)(see FIG. 15) is employed as a table that defines correspondence betweenthe coding level, and the maximum intra frame pixel number and storagepixel maximum number. However, a table T1 a that defines correspondencebetween the value of the level identifier and the maximum intra framepixel number (FIG. 16(a)) and a table T1 b that defines correspondencebetween the value of the level identifier and the maximum storage pixelnumber (FIG. 16(b)) may be employed in place of the table T1.

[0364] [Embodiment 6]

[0365]FIG. 11 is a block diagram for explaining a moving picturedecoding apparatus 50 b according to a sixth embodiment of the presentinvention.

[0366] This moving picture decoding apparatus 50 b according to thesixth embodiment receives a bit stream corresponding to plural picturesthat constitute a moving picture, and decodes the bit stream inpredetermined data processing units, i.e., in units of blocks. Morespecifically, the moving picture decoding apparatus 50 b decodes a bitstream Bsb that is generated by the moving picture coding apparatus 10 baccording to the second embodiment (see FIG. 14(b)). Therefore, in thissixth embodiment, the bit stream analyzer 501 analyzes headerinformation H1 and H2 to extract a level identifier Lst and anidentification number signal Cid, and analyzes a sequence data part Dsqto extract information Ms of a coding mode, coded data Cd, motion vectorinformation Mb, input image size information Ipx and the like,corresponding to each macroblock.

[0367] Further, the level analyzer 509 b in the moving picture decodingapparatus 50 b according to the sixth embodiment contains the tables T1and T2, and outputs maximum intra frame pixel number information Ifpxand storage pixel maximum number information Ispx on the basis of thelevel signal Lst from the bit stream analyzer 501, as well as outputspixel number calculation coefficient information a px on the basis ofthe identification number signal Cid from the bit stream analyzer 501. Adecoding capability judgment unit 506 b according to the sixthembodiment judges whether decoding of an inputted bit stream Bsb ispossible or not on the basis of the maximum intra frame pixel numberinformation Ifpx and the pixel number calculation coefficientinformation αpx from the level analyzer 509 b, and the input image sizeinformation Ipx from the bit stream analyzer 501. Here, the pixel numbercalculation coefficient information αpx is composed of information αhpxindicating a vertical pixel number calculation coefficient (Nαhxp), andinformation αwpx indicating a horizontal pixel number calculationcoefficient (Nαwpx).

[0368] Constructions of the other components of the moving picturedecoding apparatus 50 b according to the sixth embodiment are the sameas those of the moving picture decoding apparatus 50 a according to thefifth embodiment.

[0369] A specific construction of the decoding capability judgment unit506 b in the moving picture decoding apparatus 50 b according to thesixth embodiment is identical to that of the coding capability judgmentunit 108 b in the moving picture coding apparatus 100 b according to thesecond embodiment as shown in FIG. 5.

[0370] Next, the operation will be described.

[0371] The operation of the moving picture decoding apparatus 50 baccording to the sixth embodiment is different from the operation of themoving picture decoding apparatus 50 a according to the fifth embodimentonly in the operations of the bit stream analyzer 501, the decodingcapability judgment unit 506 b, and the level analyzer 509 b.

[0372] Then, the operations of the bit stream analyzer 501, the decodingcapability judgment unit 506 b, and the level analyzer 509 b will bemainly described hereinafter.

[0373] When the bit stream Bsb is inputted to the moving picturedecoding apparatus 50 b, the bit stream analyzer 501 analyzes the bitstream Bsb, and extracts various kinds of information such as codingmode information Ms, motion vector information MV, and coded data Cdfrom the bit stream Bsb. At that time, various kinds of headerinformation included in the header area Hb of the bit stream Bsb issimultaneously extracted, and inputted to the level analyzer 509 b, thedecoding capability judgment unit 506 b, and the maximum referencepicture calculator 507 a.

[0374] The level analyzer 509 b outputs maximum intra frame pixel numberinformation Ifpx and storage pixel maximum number information Ispx inaccordance with a level identifier (level signal) Lst corresponding tothe header information (code) H1 in the header area Hb, with referringto the table T1 (FIG. 15) that is held therein. The level analyzer 509 boutputs pixel number calculation coefficient information αpx (verticalpixel number calculation coefficient information αhpx and horizontalpixel number calculation coefficient information αwpx) in accordancewith the identification number signal Cid corresponding to the headerinformation (code) H2 in the header area Hb, with referring to the tableT2 (FIG. 17(a)) that is held therein. The maximum intra frame pixelnumber information Ifpx and the pixel number calculation coefficientinformation αpx is inputted to the decoding capability judgment unit 506b, while the maximum storage pixel number information Ispx is inputtedto the maximum reference picture calculator 507 a.

[0375] Then, the decoding capability judgment unit 506 b judges whetherdecoding of the inputted bit stream Bsb is possible or not, on the basisof the maximum intra frame pixel number information Ifpx and the pixelnumber calculation coefficient information αpx (vertical pixel numbercalculation coefficient information a hpx and horizontal pixel numbercalculation coefficient information αwpx) from the level analyzer 509 b,and the input image size information Ipx (input image vertical pixelnumber information Ihpx and input image horizontal pixel numberinformation Iwpx) extracted from the sequence header Sh by the bitstream analyzer 501, and outputs a signal indicating the judgementresult (judgement result signal) DSjd to the control unit 510.

[0376] In this sixth embodiment, the decoding for the inputted bitstream Bsb is performed in accordance with the judgement result signalDSjd, in the same manner as the moving picture decoding apparatus 50 aaccording to the fifth embodiment.

[0377] Next, a specific operation of the decoding capability judgmentunit 506 b in the moving picture decoding apparatus 50 b will be brieflydescribed.

[0378] The decoding capability judgment unit 506 b of the moving picturedecoding apparatus 50 b according to the sixth embodiment judges thecapability or incapability of the decoding for the inputted bit streamBsb according to the above-mentioned conditional formulas (formula 1),(formula 2a), (formula 2b), (formula 8a), and (formula 8b).

[0379] Initially, the decoding capability judgment unit 506 b performsthe operation indicated by the (formula 1) on the basis of the inputimage size information Ipx (vertical pixel number information Ihpx andhorizontal pixel number information Iwpx of the input image) that isoutputted from the bit stream analyzer 501, like in the decodingcapability judgment unit 506 a according to the fifth embodiment. Inother words, multiplication for obtaining the product (h×w) of thenumber of vertical pixels (h) and the number of horizontal pixels (w) inthe input image is performed, and then comparison between themultiplication result (h×w) and the maximum intra frame pixel number(Nfpx) (i.e., intra frame pixel number comparison) is performed.

[0380] Next, the decoding capability judgment unit 506 b calculates themaximum number of vertical pixels (H) and the maximum number ofhorizontal pixels (W) as indicated by the (formula 8a) and (formula 8b),on the basis of the intra frame pixel number information Ifpx and thepixel detection coefficient information αpx (vertical pixel numbercalculation coefficient information αhpx and horizontal pixelcalculation coefficient information αwpx).

[0381] Here, the (formula 8a) and (formula 8b) indicate that the maximumnumber of vertical pixels (H) and the maximum number of horizontalpixels (W) are obtained by dividing the maximum number of intra framepixels (Nfpx) by the vertical pixel number calculation coefficient(Nαhpx) and the horizontal pixel number calculation coefficient (Nαwpx),respectively.

[0382] Further, the decoding capability judgment unit 506 b rounds themaximum vertical pixel number (H) and the maximum horizontal pixelnumber (W) to a multiple of 16, respectively, by an operation such asomission, raising, or half-adjust, and performs comparison between theinput image vertical pixel number (h) and the rounded vertical pixelmaximum number (H) (i.e., vertical pixel number comparison), andcomparison between the input image horizontal pixel number (w) and therounded horizontal pixel maximum number (W) (i.e., horizontal pixelnumber comparison).

[0383] Then, the final judgement as to the capability or incapability ofthe decoding is performed on the basis of the results of the intra framepixel number comparison, the vertical pixel number comparison, and thehorizontal pixel number comparison.

[0384] As described above, the moving picture decoding apparatus 50 baccording to the sixth embodiment includes the level analyzer unit 509 bthat decides the maximum number of intra frame pixels (Nfpx) which canbe decoded and the maximum number of storage pixels (Nspx) which can bestored in the picture memory 503, as well as the pixel numbercalculation coefficient (Nαpx), on the basis of level identifier (levelsignal) Lst and the identification number signal Cid, which areextracted from the bit stream Bsb by the bit stream analyzer 501,thereby judging whether decoding of the inputted bit stream Bsb ispossible or not on the basis of the maximum intra frame pixel number(Nfpx) and the pixel number calculation coefficient (Nαpx) which aredecided by the level analyzer 509 b, and the input image sizeinformation Ipx included in the bit stream Bsb, and calculating thenumber of reference candidate pictures (reference picture maximumnumber) Nrpn which can be referred to at the inter picture predictiondecoding. Therefore, a bit stream which can be decoded by the movingpicture decoding apparatus among bit streams which have been suppliedfrom the coding end is determined on the basis of the level identifier,whereby picture prediction decoding corresponding the picture predictioncoding on the coding end can be satisfactorily performed. Accordingly, amemory area of the decoding apparatus that is adapted to the codingmethod in which there is no restraint on the capacity of the memory areacan be designed.

[0385] In this sixth embodiment, the maximum number of vertical pixels(H) and the maximum number of horizontal pixels (W) are obtained bydividing the maximum intra frame pixel number (Nfpx) by the verticalpixel number calculation coefficient (Nαhpx) and the horizontal pixelnumber calculation coefficient (Nαwpx), respectively, whereby theprocess for obtaining the maximum number of vertical pixels (H) and themaximum number of horizontal pixels (W) can be facilitated as comparedto the fifth embodiment.

[0386] Here, in the sixth embodiment, the level identifier correspondingto the maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the identification number corresponding to thevertical pixel number calculation coefficient (Nαhpx) and the horizontalpixel number calculation coefficient (Nαwpx) are parameters thatindicate independent coding conditions, respectively. However, the valueof the identification number may be correlated with the value of thelevel identifier.

[0387] In this case, specific values of the vertical pixel numbercalculation coefficient (Nαhpx) and the horizontal pixel numbercalculation coefficient (Nαwpx) are decided together with specificvalues of the maximum intra frame pixel number (Nfpx) and the maximumstorage pixel number (Nspx) on the basis of the level signal Lstindicating the level identifier, with referring to the tables T1 and T2.That is, when the level signal Lst from the bit stream analyzer 501 isinputted to the level analyzer 509 b, the level analyzer 509 b outputsinformation Ifpx and Ispx indicating the maximum intra frame pixelnumber (Nfpx) and the maximum storage pixel number (Nspx), respectively,with reference to the table T1 on the basis of the level signal Lst, andfurther outputs pixel number calculation coefficient information αpx onthe basis of the identification number corresponding to the levelidentifier, with reference to the table T2. In this case, the bit streamBsb includes only the code H1 corresponding to the level signal Lst, andthus the identification number signal Cid corresponding to the code H2is not outputted from the bit stream analyzer 501 to the level analyzer509 b.

[0388] According to this sixth embodiment, the moving picture decodingapparatus analyzes the code H1 of the level identifier corresponding tothe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the code H2 of the identification numbercorresponding to the vertical pixel number calculation coefficient(Nαhpx) and the horizontal pixel number calculation coefficient (Nαwpx),then obtains the maximum intra frame pixel number (Nfpx) and the maximumstorage pixel number (Nspx) with reference to the table T1 on the basisof the level identifier obtained by the analysis of the code H1, andfurther obtains the vertical pixel number calculation coefficient(Nαhpx) and the horizontal pixel number calculation coefficient (Nαwpx)with reference to the table T2 on the basis of the identification numbersignal Cid obtained by the analysis of the code H2. However, the movingpicture decoding apparatus may analyze a code that is obtained by codingpixel number calculation coefficient information α px indicatingarbitrary vertical pixel number calculation coefficient (Nαhpx) andhorizontal pixel number calculation coefficient (Nαwpx), which aredecided by the user, and directly obtain the pixel number calculationcoefficient information αpx by the analysis of the code.

[0389] In this case, the decision of specific values for the maximumintra frame pixel number (Nfpx) and the maximum storage pixel number(Nspx) is performed with reference to the table T1, while the decisionof specific values for the vertical pixel number calculation coefficient(Nαhpx) and the horizontal pixel number calculation coefficient (Nαwpx)is performed by the analysis of the code corresponding to the pixelnumber calculation coefficient information αpx, without referring to thetable.

[0390] That is, when the level signal Lst from the bit stream analyzer501 is inputted to the level analyzer 509 b, the level analyzer 509 boutputs information Ifpx indicating the maximum intra frame pixel number(Nfpx) decided with reference to the table T1, to the decodingcapability judgment unit 506 b, and outputs information Ispx indicatingthe maximum storage pixel number (Nspx) decided with reference to thetable T1, to the maximum reference picture calculator 507 a, inaccordance with the level signal Lst. Further, the pixel numbercalculation coefficient information αpx indicating specific values ofthe vertical pixel number calculation coefficient (Nαhpx) and thehorizontal pixel number calculation coefficient (Nαwpx), which areobtained by the analysis of the code by the bit stream analyzer 501 isdirectly inputted to the decoding capability judgment unit 506 b.

[0391] [Embodiment 7]

[0392]FIG. 12 is a block diagram for explaining a moving picturedecoding apparatus 50 c according to a seventh embodiment of the presentinvention.

[0393] The moving picture decoding apparatus 50 c according to theseventh embodiment receives a bit stream corresponding to pluralpictures that constitute a moving picture, and decodes the bit stream inpredetermined data processing units, i.e., in units of blocks. Morespecifically, this moving picture decoding apparatus 50 c decodes a bitstream Bsc (FIG. 14(c)) that is generated by the moving picture codingapparatus 10 c according to the third embodiment. Therefore, the bitstream analyzer 501 according to the seventh embodiment analyzes headerinformation H1 and H3, to extract the level identifier Lst and theidentification number signal Sid, and analyzes data in the sequence datapart Dsq, to extract information corresponding each macroblock such ascoding mode information Ms, coded data Cd, motion vector information MV,and input image size information Ipx.

[0394] The level analyzer 509 c of the moving picture decoding apparatus50 c according to the seventh embodiment has the tables T1 and T3, andoutputs maximum intra frame pixel number information Ifpx and storagepixel maximum number information Ispx on the basis of the level signalLst outputted from the bit stream analyzer 501, as well as outputsmaximum image size information Impx on the basis of the identificationnumber signal Sid outputted from the bit stream analyzer 501. Further,the decoding capability judgment unit 506 c according to the sixthembodiment judges whether decoding of the inputted bit stream Bsc ispossible or not on the basis of the maximum intra frame pixel numberinformation Ifpx and the maximum image size information Impx from thelevel analyzer 509 c, and the input image size information Ipx from thebit stream analyzer 501. Here, the maximum image size information Impxis composed of information Imhpx indicating the maximum number ofvertical pixels (H) and information Imwpx indicating the maximum numberof horizontal pixels (W).

[0395] Constructions of the other components in the moving picturedecoding apparatus 50 c according to the seventh embodiment are the sameas those in the moving picture decoding apparatus 50 a according to thefifth embodiment.

[0396] Further, a specific construction of the decoding capabilityjudgment unit 506 c in the moving picture decoding apparatus 50 caccording to the seventh embodiment is identical to that of the codingcapability judgment unit 108 c in the moving picture coding apparatus 10c according to the third embodiment as shown in FIG. 7.

[0397] Next, the operation will be described.

[0398] When the bit stream Bsc is inputted to the moving picturedecoding apparatus 50 c, the bit stream analyzer 501 initially analyzesthe bit stream Bsc, and extracts various kinds of information such ascoding mode information Ms, motion vector information MV, and coded dataCd, from the bit stream Bsc. At that time, various kinds of headerinformation included in the header area Hc of the bit stream Bsc aresimultaneously extracted, and outputted to the level analyzer 509 c, thedecoding capability judgment unit 506 c, and the maximum referencepicture calculator 507 a.

[0399] The level analyzer 509 c refers to the table T1 (FIG. 15) that isheld therein, and outputs maximum intra frame pixel number informationIfpx and storage pixel maximum number information Ispx in accordancewith the level signal (level identifier signal) Lst corresponding toheader information (code) H1 in the header area Hc. Further, the levelanalyzer 509 c refers to the table T3 (FIG. 18(a)) that is held therein,and outputs maximum image size information Impx (vertical pixel maximumnumber information Imhpx and horizontal pixel maximum number informationImwpx) in accordance with an identification number signal Sidcorresponding to header information (a code) H3 in the header area Hb.The maximum intra frame pixel number information Ifpx and the maximumimage size information Impx is inputted to the decoding capabilityjudgment unit 506 c, while the maximum storage pixel number informationIspx is inputted to the maximum reference picture calculator 507 a.

[0400] Then, the decoding capability judgment unit 506 b judges whetherdecoding of the inputted bit stream Bsc is possible or not, on the basisof the maximum intra frame pixel number information Ifpx and the maximumimage size information Impx (vertical pixel maximum number informationImhpx and horizontal pixel maximum number information Imwpx) from thelevel analyzer 509 c, and the input image size information Ipx (inputimage vertical pixel number information Ihpx and input image horizontalpixel number information Iwpx) that has been extracted from the sequenceheader by the bit stream analyzer 501, and outputs a signal indicatingthe judgement result (judgement result signal) Dsjd to the control unit510.

[0401] In this seventh embodiment, the decoding for the bit stream Bscis performed in accordance with the judgement result signal DSjd in thesame manner as the moving picture decoding apparatus 50 a of the fifthembodiment.

[0402] Next, a specific operation of the decoding capability judgmentunit 506 c in the moving picture decoding apparatus 50 c will be brieflydescribed.

[0403] In the decoding capability judgment unit 506 c in the movingpicture decoding apparatus 50 a according to the seventh embodiment, itis judged whether the decoding for the inputted bit stream Bsc ispossible or not, according to the conditional formulas (formula 1),(formula 2a), and (formula 2b).

[0404] Initially, the decoding capability judgment unit 506 c performsthe operation indicated by the (formula 1) on the basis of the inputimage size information Ipx (vertical pixel number information Ihpx andhorizontal pixel number information Iwpx) that is outputted from the bitstream analyzer 501, in the same manner as the decoding capabilityjudgment unit 506 a according to the fifth embodiment. That is,multiplication for obtaining the product (h×w) of the number of verticalpixels (h) and the number of horizontal pixels (w) in the input image isperformed, and comparison between the multiplication result (h×w) andthe maximum number of intra frame pixels (Nfpx) (i.e., intra frame pixelnumber comparison) is performed.

[0405] Then, on the basis of the maximum image size information Impx(vertical pixel maximum number information Imhpx and horizontal pixelmaximum number information Imwpx), the decoding capability judgment unit506 c performs comparison between the input image vertical pixel number(h) and the maximum vertical pixel number (H) indicated by the maximumvertical pixel number information Imhpx (i.e., vertical pixel numbercomparison), and comparison between the input image horizontal pixelnumber (w) and the maximum horizontal pixel number (W) indicated by themaximum horizontal pixel number information Imwpx (i.e., horizontalpixel number comparison).

[0406] Then, the final judgement as to the capability or incapability ofdecoding is performed on the basis of the results of the intra framepixel number comparison, the vertical pixel number comparison, and thehorizontal pixel number comparison.

[0407] As described above, the moving picture decoding apparatus 50 caccording to the seventh embodiment includes the level analyzer 509 cthat decides the maximum number of intra frame pixels (Nfpx) which canbe decoded and the maximum number of storage pixels (Nspx) which can bestored in the picture memory 503 and decides the maximum image size(Nmpx) as well as decides the maximum image size (Nmpx), on the basis ofthe level identifier (level signal) Lst and the identification numbersignal Sid, which are extracted from the bit stream Bsc by the bitstream analyzer 501, thereby judging whether the decoding for theinputted bit stream Bsc is possible or not on the basis of the maximumintra frame pixel number (Nfpx) and the maximum image size (Nmpx) whichare decided by the level analyzer 509 c, and the input image sizeinformation Ipx included in the bit stream Bsc, and calculating thenumber of reference candidate pictures which can be referred to at theinter picture prediction decoding (reference picture maximum number)Nrpn. Therefore, bit streams which can be decoded by the moving picturedecoding apparatus among bit streams which have been supplied from thecoding end can be determined on the basis of the level identifier,whereby picture prediction decoding corresponding to the pictureprediction coding on the coding end can be satisfactorily performed.Accordingly, a memory area of a decoding apparatus that is adapted tothe coding method in which there is no restraint on the capacity of thememory area can be designed.

[0408] In this seventh embodiment, the maximum number of vertical pixels(H) and the maximum number of horizontal pixels (W) are obtained on thebasis of the maximum image size information Impx included in the bitstream Bsc. Therefore, the process for obtaining the maximum number ofvertical pixels (H) and the maximum number of horizontal pixels (W) isfacilitated as compared to the fifth embodiment.

[0409] In this seventh embodiment, the level identifier corresponding tothe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the identification number corresponding to themaximum number of vertical pixels (H) and the maximum number ofhorizontal pixels (W) are parameters that indicate independent codingconditions, respectively. However, values of the identification numbercan be correlated with values of the level identifier.

[0410] In this case, specific values of the maximum number of verticalpixels (H) and the maximum number of horizontal pixels (W) are decidedtogether with specific values of the maximum number of intra framepixels (Nfpx) and the maximum number of storage pixels (Nspx) inaccordance with the level signal Lst indicating the level identifierwith reference to the tables T1 and T3. That is, when the level signalLst from the bit stream analyzer 501 is inputted to the level analyzer509 c, the level analyzer 509 c outputs information Ifpx and Ispxindicating the intra frame maximum number (Nfpx) and the maximum storagepixel number (Nspx), respectively, with reference to the table T1 on thebasis of the level signal Lst, and further outputs the maximum imagesize information Impx with reference to the table T3 on the basis of theidentification number corresponding to the level identifier. In thiscase, the bit stream Bsc includes only the code Hc corresponding to thelevel signal Lst, and thus the identification number signal Sidcorresponding to the code H3 is not outputted from the bit streamanalyzer 501 to the level analyzer 509 c.

[0411] Further, in the seventh embodiment, the moving picture decodingapparatus analyzes the code H1 of the level identifier corresponding tothe maximum intra frame pixel number (Nfpx) and the maximum storagepixel number (Nspx), and the code H3 of the identification numbercorresponding to the maximum number of vertical pixels (H) and themaximum number of horizontal pixels (W), then obtains the inter-framepixel maximum number (Nfpx) and the maximum storage pixel number (Nspx)from the table T1 on the basis of the level identifier obtained by theanalysis of the code H1, and obtains the maximum number of verticalpixels (H) and the maximum number of horizontal pixels (W) from thetable T3 on the basis of the identification number signal Sid obtainedby the analysis of the code H3. However, the moving picture decodingapparatus may analyze a code that is obtained by coding the maximumimage size information Impx indicating arbitrary vertical pixel maximumnumber (H) and horizontal pixel maximum number (W) which are decided bythe user, and obtain the maximum image size information Impx directly bythe analysis of the code.

[0412] In this case, decision of specific values of the intra framemaximum pixel number (Nfpx) and the maximum storage pixel number (Nspx)is performed on the basis of the table T1, while decision of specificvalues of the maximum vertical pixel number (H) and horizontal pixelmaximum number (W) is performed by the analysis of the codecorresponding to the maximum image size information Impx, without usingany table.

[0413] In other words, when the level signal Lst from the bit streamanalyzer 501 is inputted to the level analyzer 509 c, the level analyzer509 c outputs information Ifpx indicating the maximum intra frame pixelnumber (Nfpx), which is decided on the basis of the table T1, to thedecoding capability judgment unit 506 c, and outputs information Ispxindicating the maximum storage pixel number (Nspx), which is decided onthe basis of the table T1, to the maximum reference picture calculator507 a, in accordance with the level signal Lst. Further, the maximumimage size information Impx indicating specific values of the maximumvertical pixel number (H) and the maximum horizontal pixel number (W),which is obtained by the analysis of the code in the bit stream analyzer501 is directly inputted to the coding capability judgment unit 506 c.

[0414] [Embodiment 8]

[0415]FIG. 13 is a block diagram for explaining a moving picturedecoding apparatus 50 d according to an eighth embodiment of the presentinvention.

[0416] The moving picture decoding apparatus 50 d of the eighthembodiment receives a bit stream corresponding to plural pictures thatconstitute a moving picture, and decodes the bit stream in predetermineddata processing units, i.e., in units of blocks. More specifically, themoving picture decoding apparatus 50 d decodes a bit stream Bsa (FIG.14(a)) which is generated by the moving picture coding apparatus 10 d,according to the fourth embodiment. However, the bit stream generatedby the moving picture coding apparatus 10 d of the fourth embodiment hasthe same data structure as that of the bit stream generated by themoving picture coding apparatus 10 a of the first embodiment, andaccordingly the moving picture decoding apparatus 50 d can also decodethe bit stream generated by the moving picture coding apparatus 10 a ofthe first embodiment.

[0417] That is, the moving picture decoding apparatus 50 d according tothe eighth embodiment has, in place of the maximum reference picturecalculator 507 a in the moving picture decoding apparatus 50 a accordingto the fifth embodiment, a maximum reference picture calculator 507 dthat calculates the maximum number of reference pictures (Nrpn) on thebasis of input image size information Ipx (input image vertical pixelnumber information Ihpx and input image horizontal pixel numberinformation Iwpx), maximum storage pixel number information Ispx,display wait picture number information Idwp, and outputs informationindicating the calculated value (Nrpn) (i.e., reference picture maximumnumber information) Irpn.

[0418] Here, the display wait picture number information Idwp isinformation that indicates the number of display wait pictures, and thedisplay wait picture are decoded pictures which are not employed asreference pictures but whose image data are kept stored in a picturememory of the decoding apparatus until display of these pictures isperformed, as described with reference to FIG. 26. Further, the controlof the picture memory according to the eighth embodiment is performed sothat image data of a picture that is not employed as the referencepicture is deleted from the picture memory immediately after the displayof the picture is finished.

[0419] Constructions of the other components in the moving picturedecoding apparatus 50 d according to the eighth embodiment are the sameas those in the moving picture decoding apparatus 50 a according to thefifth embodiment.

[0420] A specific construction of the maximum reference picturecalculator 507 d in the moving picture decoding apparatus 50 d accordingto the eighth embodiment is identical to that of the maximum referencepicture calculator 109 d in the moving picture coding apparatus 10 daccording to the fourth embodiment, as shown in FIG. 9.

[0421] Next, its operation will be described.

[0422] The operation of the moving picture decoding apparatus 50 daccording to the eighth embodiment is different from the operation ofthe moving picture decoding apparatus 50 a according to the fifthembodiment only in the operation of the maximum reference picturecalculator 507 d.

[0423] Hereinafter, only the operation of the maximum reference picturecalculator 507 d will be described.

[0424] The maximum reference picture calculator 507 d of the movingpicture decoding apparatus 50 d according to the eighth embodimentcalculates the maximum number of reference candidate pictures which areemployed at the inter picture prediction decoding, according to theoperation indicated by the (formula 11).

[0425] That is, in the maximum reference picture calculator 109 d, thetotal number of pixels in one frame (h×w) as the size of the input imageis calculated on the basis of the input image vertical pixel numberinformation Ihpx and the input image horizontal pixel number informationIwpx.

[0426] Next, an operation of dividing the maximum storage pixel number(Nspx) by the multiplication result (h×w) is performed, and an operationof subtracting 1 from the division result (Nspx/(h×w)) is performed.

[0427] Then, the reference picture maximum number is decided bysubtracting the number of display wait pictures (Ndwp) from thesubtraction result (Nspx/(h×w)−1).

[0428] As described above, the moving picture decoding apparatus 50 daccording to the eighth embodiment includes the level analyzer 509 athat decides the maximum number of intra frame pixels which can bedecoded (Nfpx), and the maximum number of storage pixels which can bestored in the picture memory 503 (Nspx), on the basis of the levelidentifier indicated by the level signal Lst which is extracted from thebit stream Bsa by the bit stream analyzer 501, thereby performingjudgement as to the capability or incapability of decoding for theinputted bit stream Bsa on the basis of the maximum intra frame pixelnumber (Nfpx) and the input image size (the number of vertical pixelsNhpx and the number of horizontal pixels Nwpx), as well as calculatingthe number of reference candidate pictures which can be referred to atthe inter picture prediction decoding (reference picture maximum number)Nrpn. Therefore, a bit stream which can be decoded by the moving picturedecoding apparatus, among bit streams supplied from the coding end canbe determined by the level identifier, thereby satisfactorily performingpicture prediction decoding corresponding to the picture predictioncoding on the coding end. Accordingly, a memory area in the decodingapparatus corresponding to the coding method in which there is norestraint on the capacity of the memory area can be designed.

[0429] In this eighth embodiment, the maximum number of referencepictures which are stored in the picture memory is decided in view ofthe number of display wait pictures (Ndwp). Therefore, the picturememory in which image data of reference candidate pictures are storedcan be efficiently utilized depending on the status of processing forimage data.

[0430] Here, in the eighth embodiment, the control of the picture memoryis performed so that image data of a picture which is not employed as areference picture are deleted from the picture memory immediately afterdisplay of the picture is finished. However, the image data of a picturethat is not employed as the reference picture may be deleted in timingother than immediately after the display as described in the eighthembodiment.

[0431] For example, the control of the picture memory in the eighthembodiment may be performed so that image data of a picture that isstored in the picture memory but is not employed as the referencepicture are deleted from the picture memory after a display time of onepicture expires after the picture has been displayed. In this case, theimage data of the display wait picture are kept stored in the picturememory for a predetermined time period after the picture has beendisplayed.

[0432] Further, in the first to eighth embodiments, the moving picturecoding apparatus or the moving picture decoding apparatus is implementedby hardware, while the moving picture coding apparatus or the movingpicture decoding apparatus may be implemented by software. In this case,by recording a program for executing the coding processing or thedecoding processing as described in any of the above embodiments, in adata storage medium such as a flexible disk, the moving picture codingapparatus or the moving picture decoding apparatus can be constructed inan independent computer system.

[0433]FIG. 19 are diagrams for explaining a system which implements themoving picture coding apparatus according to any of the first to fourthembodiments or the moving picture decoding apparatus according to any ofthe fifth to eighth embodiments, with a computer system, by utilizing aflexible disk that contains the program.

[0434]FIG. 19(b) shows the front view of a flexible disk, thecross-sectional view thereof, and a flexible disk body, and FIG. 19(a)shows an example of a physical format of the flexible disk as a storagemedium body. To be specific, the flexible disk body FD is contained inthe flexible disk case F. On the surface of the flexible disk body,plural tracks Tr are concentrically formed from the outer circumferencetoward the inner circumference. Each track Tr is divided into 16 sectorsSe in the angular direction. Accordingly, in the flexible disk in whichthe above-described program is stored, data of the program are recordedin the sectors assigned onto the flexible disk body FD.

[0435]FIG. 19(c) shows a construction for recording or reproducing theprogram on/from the flexible disk FD. When the program is written in theflexible disk FD, data of the program supplied from a computer system Csare written in the flexible disk FD via a flexible disk drive. When themoving picture coding apparatus or the moving picture decoding apparatusis constructed in the computer system Cs using the program recorded onthe flexible disk, the program is read from the flexible disk by theflexible disk drive, and loaded onto the computer system.

[0436] While in the above description a flexible disk is employed as thedata storage medium, an optical disk may be employed as the data storagemedium. Also in this case, the moving picture coding apparatus or themoving picture decoding apparatus can be implemented by a computersystem. Further, the data storage medium is not restricted to theoptical disk and the flexible disk. Any medium, such as an IC card or aROM cassette, may be employed so long as the program can be stored inthe medium.

[0437] Hereinafter, applications of the moving picture coding apparatusor the moving picture decoding apparatus according to any of theaforementioned embodiments, and systems using the application will bedescribed hereinafter.

[0438]FIG. 20 is a block diagram illustrating an entire construction ofa contents provision system 1100 that provides contents distributionservices.

[0439] A communication service providing area is divided into regions(cells) of desired size, and base stations 1107 to 1110 which are eachfixed radio stations are established in the cells, respectively.

[0440] In this contents provision system 1100, various devices such as acomputer 1111, a PDA (personal digital assistant) 1112, a camera 1113, aportable phone 1114, and a portable phone with a camera 1200 areconnected, for example to the Internet 1101, through an Internet serviceprovider 1102, a telephone network 1104, and the base stations 1107 to1110.

[0441] The contents provision system 1100 is not restricted to a systemincluding all of the plural devices shown in FIG. 20, but may be oneincluding some of the plural devices shown in FIG. 20. Further, therespective devices may be connected directly to the telephone network1104, not through the base stations 1107 to 1110 as the fixed radiostations.

[0442] The camera 1113 is a device that can take moving pictures of anobject, like a digital video camera. The portable phone may be aportable phone set according to any of PDC (Personal DigitalCommunications) system, CDMA (Code Division Multiple Access) system,W-CDMA (Wideband-Code Division Multiple Access) system, and GSM (GlobalSystem for Mobile Communications) system, or PHS (Personal HandyphoneSystem).

[0443] A streaming server 1103 is connected to the camera 1113 throughthe base station 1109 and the telephone network 1104. In this system,live distribution, based on coded data which are transmitted by theuser, using the camera 1113 can be performed. The processing for codingdata of taken pictures may be carried out by either the camera 1113 orthe server that transmits the data. Moving picture data which areobtained by taking moving pictures of an object by means of the camera1116 may be transmitted to the streaming server 1103 through thecomputer 1111. The camera 1116 is a device that can take still picturesor moving pictures of an object, such as a digital camera. In this case,coding of the moving picture data can be performed by either the camera1116 or the computer 1111. Further, the coding processing is carried outby an LSI 1117 included in the computer 1111 or the camera 1116.

[0444] Image coding or decoding software may be stored in a storagemedium (a CD-ROM, a flexible disk, a hard disk, or the like), which is arecording medium containing data that is readable by the computer 1111or the like. Further, the moving picture data may be transmitted throughthe portable phone with a camera 1200. The moving picture data are datawhich have been coded by an LSI included in the portable phone 1200.

[0445] In this contents provision system 1100, contents whose picturesare taken by the user with the camera 1113 or camera 1116 (for example,live video of a music concert) are coded in the same manner as any ofthe aforementioned embodiments, and transmitted from the camera to thestreaming server 1103. The contents data are subjected to streamingdistribution from the streaming server 1103 to a requesting client.

[0446] The client may be any of the computer 1111, the PDA 1112, thecamera 1113, the portable phone 1114 and the like, which can decode thecoded data.

[0447] In this contents provision system 1100, the coded data can bereceived and reproduced on the client side. When the data are received,decoded, and reproduced in real time on the client side, privatebroadcasting can be realized.

[0448] The coding or decoding in the respective devices that constitutethis system can be performed using the moving picture coding apparatusor the moving picture decoding apparatus according to any of theaforementioned embodiments.

[0449] A portable phone will be now described as an example.

[0450]FIG. 21 is a diagram illustrating a portable phone 1200 thatutilizes the moving picture coding apparatus and the moving picturedecoding apparatus according to any of the aforementioned embodiments.

[0451] This portable phone 1200 includes an antenna 1201 fortransmitting/receiving radio waves to/from the base station 1110, acamera unit 1203 that can take video or still pictures of an object,such as a CCD camera, and a display unit 1202 such as a liquid crystaldisplay for displaying data of the video taken by the camera unit 1203or video received through the antenna 1201.

[0452] The portable phone 1200 further includes a main body 1204including plural control keys, a voice output unit 1208 for outputtingvoices such as a speaker, a voice input unit 1205 for inputting voicessuch as a microphone, a storage medium 1207 for retaining coded data ordecoded data such as data of taken moving pictures or still pictures, ordata, moving picture data or still picture data of received e-mail, anda slot unit 1206 which enables the storage medium 1207 to be attached tothe portable phone 1200.

[0453] The storage medium 1207 contains a flash memory element as a typeof EEPROM (Electrically Erasable and Programmable Read Only Memory) thatis an electrically programmable and erasable non-volatile memorycontained in a plastic case, like a SD card.

[0454] The portable phone 1200 will be described more specifically withreference to FIG. 22.

[0455] The portable phone 1200 has a main control unit 1241 thatperforms general control for the respective units of the main bodyincluding the display unit 1202 and the control key 1204.

[0456] The portable phone 1200 further includes a power supply circuit1240, an operation input control unit 1234, an image coding unit 1242, acamera interface unit 1233, a LCD (Liquid Crystal Display) control unit1232, an image decoding unit 1239, a multiplexing/demultiplexing unit1238, a recording/reproduction unit 1237, a modulation/demodulation unit1236, and an audio processing unit 1235. The respective units of theportable phone 1200 are connected to each other via a synchronizationbus 1250.

[0457] The power supply circuit 1240 supplies power from a battery packto the respective units when a call end/power supply key is turned ONunder the control of the user, thereby activating the digital portablephone with a camera 1200 to be turned into an operable state.

[0458] In the portable phone 1200, the respective units operate undercontrol of the main control unit 1241 that is constituted by a CPU, aROM, a RAM and the like. To be more specific, in the portable phone1200, an audio signal that is obtained by voice inputting into the voiceinput unit 1205 in a voice communication mode is converted into digitalaudio data by the audio processing unit 1235. The digital audio data aresubjected to a spectrum spread process by the modulation/demodulationcircuit 1236, further subjected to a D/A conversion process and afrequency transformation process by the transmission/receiving circuit1231, and transmitted through the antenna 1201.

[0459] In this portable phone set 1200, a signal received through theantenna 1201 in the voice communication mode is amplified, and thensubjected to a frequency transformation process and an A/D conversionprocess. The received signal is further subjected to a spectrum inversespread process in the modulation/demodulation circuit 1236, convertedinto an analog audio signal by the audio processing unit 1235, and thisanalog audio signal is outputted through the voice output unit 1208.

[0460] When the portable phone 1200 transmits electronic mail in a datacommunication mode, text data of the e-mail that is inputted bymanipulation of the control key 1204 on the main body are transmitted tothe main control unit 1241 via the operation input control unit 1234.The main control unit 1241 controls the respective units so that thetext data are subjected to the spectrum spread process in themodulation/demodulation circuit 1236, then subjected to the D/Aconversion process and the frequency transformation process in thetransmission/receiving circuit 1231, and thereafter transmitted to thebase station 1110 through the antenna 1201.

[0461] When this portable phone 1200 transmits image data in the datacommunication mode, data of a picture taken by the camera unit 1203 aresupplied to the image coding unit 1242 via the camera interface unit1233. When the portable phone 1200 does not transmit the image data, thedata of the picture taken by the camera unit 1203 can be displayeddirectly on the display unit 1202 via the camera interface unit 1233 andthe LCD control unit 1232.

[0462] The image coding unit 1242 includes the moving picture codingapparatus according to any of the aforementioned embodiments. This imagecoding unit 1242 compressively encodes the image data supplied from thecamera unit 1203 by the moving picture coding method according to any ofthe above embodiments to convert the same into coded image data, andoutputs the obtained coded image data to the multiplexing/demultiplexingunit 1238. At the same time, the portable phone 1200 transmits voiceswhich have been inputted to the voice input unit 1205 while the picturehas been taken by the camera unit 1203, as digital audio data, to themultiplexing/demultiplexing unit 1238 through the audio processing unit1235.

[0463] The multiplexing/demultiplexing unit 1238 multiplexes the codedimage data supplied from the image coding unit 1242 and the audio datasupplied from the audio processing unit 1235 by a predetermined method.Resultant multiplexed data are subjected to a spectrum spread process inthe modulation/demodulation circuit 1236, then further subjected to theDA conversion process and the frequency transformation process in thetransmission/receiving circuit 1231, and obtained data are transmittedthrough the antenna 1201.

[0464] When the portable phone 1200 receives data of a moving picturefile that is linked to a home page or the like in the data communicationmode, a signal received from the base station 1110 through the antenna1201 is subjected to a spectrum inverse spread process by themodulation/demodulation circuit 1236, and resultant multiplexed data aretransmitted to the multiplexing/demultiplexing unit 1238.

[0465] When the multiplexed data that have been received via the antenna1201 are decoded, the multiplexing/demultiplexing unit 1238demultiplexes the multiplexed data to divide the data into a coded bitstream corresponding to the image data and a coded bit streamcorresponding to the audio data, and the coded image data are suppliedto the image decoding unit 1239 and the audio data are supplied to theaudio processing unit 1235, via the synchronization bus 1250.

[0466] The image decoding unit 1239 includes the moving picture decodingapparatus according to any of the aforementioned embodiments. The imagedecoding unit 1239 decodes the coded bit stream of the image data by thedecoding method corresponding to the coding method according to any ofthe above-mentioned embodiments, to reproduce moving picture data, andsupplies the reproduced data to the display unit 1202 through the LCDcontrol unit 1232. Thereby, for example, the moving picture dataincluded in the moving picture file that is linked to the home page isdisplayed. At the same time, the audio processing unit 1235 converts theaudio data into an analog audio signal, and thereafter supplies theanalog audio signal to the voice output unit 1208. Thereby, for example,reproduction of the audio data included in the moving picture file thatis linked to the home page is performed.

[0467] The system to which the moving picture coding method and themoving picture decoding method according to any of the aforementionedembodiments is applicable is not restricted to the above-mentionedcontents provision system.

[0468] Recently, digital broadcasting using satellites or terrestrialwaves is talked frequently, and the moving picture coding apparatus andthe moving picture decoding apparatus according to the above embodimentsis applicable also to a digital broadcasting system 1400 as shown inFIG. 23.

[0469] More specifically, a coded bit stream corresponding to videoinformation is transmitted from a broadcast station 1409 to a satellite1410 such as a communication satellite or a broadcast satellite, viaradio communication. When the broadcast satellite 1410 receives thecoded bit stream corresponding to the video information, the satellite1410 outputs broadcasting waves, and these waves are received by anantenna 1406 at home that is provided with satellite broadcast receivingfacility. For example, an apparatus such as a television (receiver) 1401or a set top box (STB) 1407 decodes the coded bit stream, and reproducesthe video information.

[0470] Further, the moving picture decoding apparatus according to anyof the aforementioned embodiments can be mounted also on a reproductionapparatus 1403 that can read and decode the coded bit stream recorded ona storage medium 1402 such as a CD or a DVD (recording medium).

[0471] In this case, reproduced video is displayed on a monitor 1404.The moving picture decoding apparatus may be mounted on the set top box1407 that is connected to a cable 1405 for cable television or anantenna 1406 for satellite/terrestrial broadcast, to reproduce theoutput of the moving picture decoding apparatus to be displayed on amonitor 1408 of the television. In this case, the moving picturedecoding apparatus may be incorporated not in the set top box but in thetelevision. A vehicle 1412 having an antenna 1411 can receive a signalfrom the satellite 1410 or the base station 1107 (see FIG. 20), andreproduce a moving picture to be displayed on a display device of a carnavigation system 1413 or the like which is mounted on the vehicle 1412.

[0472] Further, it is also possible that an image signal can be coded bythe moving picture coding apparatus according to any of theaforementioned embodiments, and recorded in a recording medium.

[0473] A specific example of a recording device is a recorder 1420 suchas a DVD recorder that records image signals on a DVD disk 1421, and adisk recorder that records image signals on a hard disk. The imagesignals may be recorded on a SD card 1422. Further, when the recorder1420 includes the moving picture decoding apparatus according to any ofthe aforementioned embodiments, the image signals which are recorded onthe DVD disk 1421 or the SD card 1422 can be reproduced by the recorder1420 and displayed on the monitor 1408.

[0474] Here, the structure of the car navigation system 1413 mayinclude, for example, the components of the portable phone shown in FIG.22, other than the camera unit 1203, the camera interface unit 1233 andthe image coding unit 1242. The same apply to the computer 1111 (seeFIG. 20), or the television (receiver) 1401.

[0475] Further, as the terminal such as the portable phone 1114 (seeFIG. 20), one of three types of terminals: a transmission-receiving typeterminal having both of an encoder and a decoder, a transmissionterminal having only an encoder, and a receiving terminal having only adecoder, can be mounted.

[0476] As described above, the moving picture coding apparatus or themoving picture decoding apparatus according to any of the aforementionedembodiments is applicable to any of the above-mentioned devices orsystems, whereby the effects as described in the above embodiments canbe obtained.

[0477] Further, it goes without saying that the embodiments and theirapplications of the present invention are not restricted to those shownin this description.

[0478] Industrial Availability

[0479] The moving picture coding method and the moving picture decodingmethod according to the present invention can set the maximum number ofintra frame pixels for a picture which can be coded or decoded, at anoptimum value selected from plural values that have been set stepwisedepending on the coding level, in accordance with the specifications ofthe apparatus, whereby the memory area of the coding apparatus and thedecoding apparatus that are adapted to a coding method in which there isno restraint on the capacity of the memory area can be designed, whichis useful in designing the moving picture coding apparatus and themoving picture decoding apparatus.

1. A method for coding a moving picture which consists of a plurality ofpictures each consisting of a prescribed number of pixels, according toa selected coding level, including: a step of judging whether it ispossible to code the moving picture, on the basis of the maximum numberof intra frame pixels for a picture, which number conforms with theselected coding level; and a step of coding the moving picture that hasbeen judged encodable in the judging step, for each picture, to generatea code sequence for the moving picture; wherein the code sequenceincludes a code of a level identifier that identifies the maximum numberof intra frame pixels for a picture that conforms with the selectedcoding level, and the maximum number of storage pixel numbercorresponding to the data amount that can be stored in a picture memory,which conforms with the selected coding level; and the vertical pixelnumber and the horizontal pixel number of a picture constituting themoving picture that has been judged encodable in the judgement stepsatisfy predetermined conditions dependent on the level identifier. 2.The moving picture coding method of claim 1, wherein the coding stepperforms an inter picture prediction coding to a target picture to becoded, using a coded picture as a reference picture, where the maximumreference picture number that is the maximum number of referencecandidate pictures serving as candidates for the reference picture,which pictures can be stored in the picture memory, is calculated on thebasis of the vertical pixel number and the horizontal pixel number ofthe target picture as well as the level identifier.
 3. The movingpicture coding method of claim 1, wherein the vertical pixel number (h)and the horizontal pixel number (w) of a picture included in the movingpicture that has been judged encodable satisfy all following conditions,i.e., (condition 1) to (condition 3): (condition 1) h×w<=(the maximumnumber of intra frame pixel number) (condition 2) h<=round1 (H)(condition 3) w<=round2 (W) where H denotes the maximum number amongvertical pixel numbers in the picture which can be coded, W denotes themaximum number among horizontal pixel numbers in the picture which canbe coded, round10( ) denotes a value that is obtained by an operation ofrounding an argument in parentheses to a multiple of the vertical pixelnumber in a macroblock which is a unit for coding a picture, and round2() denotes a value that is obtained by an operation of rounding anargument in parentheses to a multiple of the horizontal pixel number inthe macroblock.
 4. The moving picture coding method of claim 3, whereinthe round1( ) and round2( ) each denotes a value which is obtained by anoperation of rounding an argument in parentheses to a multiple of
 16. 5.The moving picture coding method of claim 2, wherein the maximumreference picture number for the target picture is determined by afollowing formula: (the maximum reference picture number)=(the maximumstorage pixel number)÷(h×w)−1 where h denotes the vertical pixel numberin the target picture, w denotes the horizontal pixel number in thetarget picture, and the maximum storage pixel number is the total numberof the pixel numbers of the reference candidate pictures and of thetarget picture to be decoded, which pictures are stored in a picturememory in the decoding apparatus.
 6. The moving picture coding method ofclaim 2, wherein the maximum reference picture number for the targetpicture is determined by a following formula: (the maximum referencepicture number)=(the maximum storage pixel number)÷(h×w)−1−(the numberof display waiting decoded pictures) where h denotes the vertical pixelnumber in the target picture, w denotes the horizontal pixel number inthe target picture, and the maximum storage pixel number is the totalnumber of the pixel numbers of, reference candidate pictures, the targetpicture to be decoded, and display waiting decoded pictures, whichpictures are stored in a picture memory of the decoding apparatus. 7.The moving picture coding method of claim 3, wherein the maximumvertical pixel number and the maximum horizontal pixel number arecalculated using following two formula: H=sqrt (h×w×N) W=sqrt (h×w×N),where h denotes the vertical pixel number in the target picture, wdenotes the horizontal pixel number in the target picture, H denotes themaximum number among the vertical pixel numbers over pictures which canbe coded, W denotes the maximum number among the horizontal pixelnumbers over the pictures which can be coded, N denotes an arbitrarynatural number, and sqrto denotes a positive square root of an argumentin parentheses.
 8. The moving picture coding method of claim 7, whereinthe natural number N is
 8. 9. The moving picture coding method of claim3, wherein the maximum vertical pixel number and the maximum horizontalpixel number are calculated using following two formulae: H=(the maximumintra frame pixel number)÷(vertical pixel number calculationcoefficient) W=(the maximum intra frame pixel number)÷(horizontal pixelnumber calculation coefficient) where H denotes the maximum verticalpixel number among pictures which can be coded, W denotes the maximumhorizontal pixel number among pictures which can be coded, and thevertical pixel number calculation coefficient and the horizontal pixelnumber calculation coefficient are predetermined values.
 10. The movingpicture coding method of claim 3, wherein the maximum vertical pixelnumber and the maximum horizontal pixel number are decided withreferring to a previously defined table.
 11. A method for decoding acode sequence corresponding to a moving picture which consists of pluralpictures each consisting of a prescribed number of pixels, in accordancewith a level identifier for identifying a selected coding level, whichis extracted from the code sequence, including: a step of judgingwhether it is possible to decode the code sequence or not, on the basisof the maximum intra frame pixel number for a picture, which number isdependent on the coding level indicated by the level identifier, and themaximum storage pixel number which is an amount of data which can bestored in a picture memory and is dependent on the coding level; and astep of decoding the code sequence that has been judged decodable in thejudgement step, for each picture, to generate image data for the movingpicture; wherein the vertical pixel number and the horizontal pixelnumber of a picture presented by the code sequence that has been judgeddecodable in the judgement step satisfy predetermined conditions whichare provided according to the level identifier.
 12. The moving picturedecoding method of claim 11, wherein the judgment step performs judgmentof whether it is possible to decode the target code sequence or not, onthe basis of the result of comparison between unique conditions providedin the decoding apparatus, and the maximum intra frame pixel number andthe maximum storage pixel number both corresponding to the coding levelindicated by the level identifier which is extracted from the codesequence.
 13. The moving picture decoding method of claim 11, whereinthe decoding step subjects a target code sequence to an inter pictureprediction decoding, using decoded pictures as reference pictures, andthe maximum reference picture number which is the maximum number ofreference candidate pictures serving as a candidate for a referencepicture, which can be stored in the picture memory, is calculated on thebasis of the vertical pixel number and the horizontal pixel number forthe target picture as well as the level identifier.
 14. The movingpicture decoding method of claim 11, wherein the vertical pixel number(h) and the horizontal pixel number (w) of a picture corresponding tothe bit stream that has been judged decodable satisfy all followingconditions, i.e., (condition 4) to (condition 6): (condition 4)h<=round1 (H) (condition 5) w<=round2 (W) (condition 6) h×w<=(themaximum intra frame pixel number) where H denotes the maximum numberamong vertical pixel numbers of pictures that can be decoded, W denotesthe maximum number among horizontal pixel numbers of pictures that canbe decoded, round1 ( ) denotes a value that is obtained by an operationof rounding an argument in parentheses to a multiple of the verticalpixel number in a macroblock serving as a unit for decoding a picture,and round2( ) denotes a value that is obtained by an operation ofrounding an argument in parentheses to a multiple of the horizontalpixel number in the above-described macroblock.
 15. The moving picturedecoding method of claim 14, wherein the round1( ) and round2( ) eachdenotes a value which is obtained by an operation of rounding anargument in parentheses to a multiple of
 16. 16. The moving picturedecoding method of claim 12, wherein the maximum reference picturenumber for the target picture is determined by following formulae: (themaximum reference picture number)=(the maximum storage pixelnumber)÷(h×w)−1 where h denotes the vertical pixel number in the targetpicture to be decoded, w denotes the horizontal pixel number in thetarget picture to be decoded, and the maximum storage pixel numberdenotes the total number of, the pixel numbers of the referencecandidate pictures and the pixel number of the target picture to bedecoded, these pictures being stored in a picture memory of the decodingapparatus.
 17. The moving picture decoding method of claim 12, whereinthe maximum reference picture number for the target picture isdetermined by a following formula: (the maximum reference picturenumber)=(the maximum storage pixel number)÷(h×w)−1−(the number ofdisplay waiting decoded pictures) where h denotes the vertical pixelnumber in the target picture to be decoded, w denotes the horizontalpixel number in the target picture to be decoded, and the maximumstorage pixel number is the total number of the pixel numbers of, thereference candidate pictures, the target picture to be decoded, anddisplay waiting decoded pictures, these pictures being stored in apicture memory of the decoding apparatus.
 18. The moving picturedecoding method of claim 14, wherein the maximum vertical pixel numberand the maximum horizontal pixel number are calculated using followingtwo formulae: H=sqrt (h×w×N) W=sqrt (h×w×N), where h denotes thevertical pixel number in the target picture, w denotes the horizontalpixel number in the target picture, H denotes the maximum number amongvertical pixel numbers of pictures which can be decoded, W denotes themaximum number among horizontal pixel numbers of pictures which can bedecoded, N denotes an arbitrary natural number, sqrt() denotes apositive square root of an argument in parentheses.
 19. The movingpicture decoding method of claim 18, wherein the natural number N is 8.20. The moving picture decoding method of claim 14, wherein the maximumvertical pixel number and the maximum horizontal pixel number arecalculated using following two formula: H=(the maximum intra frame pixelnumber)÷(vertical pixel number calculation coefficient) W=(the maximumintra frame pixel number)÷(horizontal pixel number calculationcoefficient) where H denotes the maximum number among vertical pixelnumbers in pictures which can be decoded, and W denotes the maximumnumber among horizontal pixel numbers in pictures which can be decoded.21. The moving picture decoding method of claim 14, wherein the maximumvertical pixel number and the maximum horizontal pixel number aredecided with referring to a previously defined table.
 22. A data storagemedium that contains a program for implementing a process of coding amoving picture, where the program makes a computer execute the codingprocess according to the moving picture coding method of any of claims 1to
 10. 23. A data storage medium that contains a program forimplementing a process of decoding a code sequence corresponding to amoving picture, where the program makes a computer execute the decodingprocess according to the moving picture decoding method of any of claims11 to 21.